creation magnified reduced images real imaginary including case chirality images alhazen ibn al haytham father optics ibn sahl 's manuscript showing knowledge law refraction middle ages greek ideas optics resurrected extended writers muslim world one earliest al kindi c wrote merits aristotelian euclidean ideas optics favouring emission theory since could better quantify optical phenomena persian mathematician ibn sahl wrote treatise burning


mirrors lenses correctly describing law refraction equivalent snell 's law ref name j ref used law compute optimum shapes lenses curved mirrors early th century alhazen ibn al haytham wrote ''book optics'' ''kitab al manazir'' explored reflection refraction proposed new system explaining vision light based observation experiment rejected emission theory ptolemaic optics rays emitted eye instead put forward idea light reflected directions straight lines points


objects viewed entered eye although unable correctly explain eye captured rays alhazen 's work largely ignored arabic world anonymously translated latin around ad summarised expanded polish monk witelo making standard text optics europe next years th century medieval europe english bishop robert grosseteste wrote wide range scientific topics discussed light four different perspectives epistemology light metaphysics cosmogony


polishing lenses spectacles first venice florence thirteenth century later spectacle making centres netherlands germany spectacle makers created improved types lenses correction vision based empirical knowledge gained observing effects lenses rather using rudimentary optical theory day theory part could even adequately explain spectacles worked practical development mastery experimentation lenses led directly invention compound optical microscope around refracting telescope


recorded images finally able scientifically quantify effects different types lenses spectacle makers observing previous years invention telescope kepler set theoretical basis worked described improved version known ''keplerian telescope'' using two convex lenses produce higher magnification cover first edition newton 's ''opticks'' optical theory progressed mid th century treatises written philosopher ren descartes explained variety optical phenomena including reflection refraction assuming light


emitted objects produced ref name sabra ref differed substantively ancient greek emission theory late early isaac newton expanded descartes' ideas corpuscle theory light famously determining white light mix colours separated component parts prism christiaan huygens proposed wave theory light based suggestions made robert hooke hooke publicly criticised newton 's theories light feud two lasted hooke 's death newton published ''opticks''


time partly success areas physics generally considered victor debate nature light ref name sabra newtonian optics generally accepted early th century thomas young augustin jean fresnel conducted experiments interference light firmly established light 's wave nature young 's famous double slit experiment showed light followed superposition principle wave like property predicted newton 's corpuscle theory work led theory diffraction light opened entire area


study physical optics wave optics successfully unified electromagnetic theory james clerk maxwell next development optical theory came max planck correctly modelled blackbody radiation assuming exchange energy light matter occurred discrete amounts called ''quanta'' albert einstein published theory photoelectric effect firmly established quantization light ref name annphysik ref niels bohr showed atoms could emit discrete amounts energy thus explaining discrete lines seen emission absorption spectra


understanding interaction light matter followed developments formed basis quantum optics also crucial development quantum mechanics whole ultimate culmination theory quantum electrodynamics explains optics electromagnetic processes general result exchange real virtual photons quantum optics gained practical importance inventions maser laser following work paul dirac quantum field theory george sudarshan roy j glauber leonard mandel applied quantum


optics geometry reflection refraction light rays''geometrical optics'' ''ray optics'' describes propagation light terms rays travel straight lines whose paths governed laws reflection refraction interfaces different media laws discovered empirically far back ad ref name j used design optical components instruments present day summarised follows ray light hits boundary two transparent materials divided reflected


refracted ray law reflection says reflected ray lies plane incidence angle reflection equals angle incidence law refraction says refracted ray lies plane incidence sine angle incidence divided sine angle refraction constant math frac sin theta sin theta n math constant two materials given colour light first material air vacuum refractive index second material


laws reflection refraction derived fermat 's principle states ''the path taken two points ray light path traversed least time'' approximations geometric optics often simplified making paraxial approximation small angle approximation mathematical behaviour becomes linear allowing optical components systems described simple matrices leads techniques gaussian optics ''paraxial ray tracing'' used find basic properties optical systems approximate image object positions magnifications


reflections diagram specular reflection reflections divided two types specular reflection diffuse reflection specular reflection describes gloss surfaces mirrors reflect light simple predictable way allows production reflected images associated actual real extrapolated virtual location space diffuse reflection describes non glossy materials paper rock reflections surfaces described statistically exact distribution reflected light depending microscopic structure material many diffuse reflectors described


called retroreflection mirrors curved surfaces modelled ray tracing using law reflection point surface mirrors parabolic surfaces parallel rays incident mirror produce reflected rays converge common focus curved surfaces may also focus light aberrations due diverging shape causing focus smeared space particular spherical mirrors exhibit spherical aberration curved mirrors form images magnification greater less one magnification negative indicating


case transmission occurs light reflected phenomenon called total internal reflection allows fibre optics technology light travels optical fibre undergoes total internal reflection allowing essentially light lost length cable ref name geoptics lenses ray tracing diagram converging lens device produces converging diverging light rays due refraction known ''lens'' lenses characterized focal length converging lens positive focal length diverging lens negative focal length smaller focal


length indicates lens stronger converging diverging effect focal length simple lens air given lensmaker 's equation ref name hecht chapters ref ray tracing used show images formed lens thin lens air location image given simple equation math frac frac frac f math math math distance object lens math math distance lens image math f math focal length lens


sign convention used object image distances positive object image opposite sides lens ref name hecht thumb incoming parallel rays focused converging lens onto spot one focal length lens far side lens called rear focal point lens rays object finite distance focused lens focal distance closer object lens image lens diverging lenses incoming


equal size real inverted image '''i''' ''f'' image infinity '''k''' ''f'' double size virtual upright image physical optics physical optics light considered propagate wave model predicts phenomena interference diffraction explained geometric optics speed light waves air approximately sup sup nbsp exactly nbsp vacuum wavelength visible light waves varies nbsp nm term light also often applied infrared nbsp ultraviolet radiation nbsp nm wave model used


make predictions optical system behave without requiring explanation waving medium middle th century physicists believed ethereal medium light disturbance propagated existence electromagnetic waves predicted maxwell 's equations waves propagate speed light varying electric magnetic fields orthogonal one another also direction propagation waves light waves generally treated electromagnetic waves except quantum mechanical effects


considered modelling design optical systems using physical optics many simplified approximations available analysing designing optical systems use single scalar quantity represent electric field light wave rather using vector model orthogonal electric magnetic vectors ref name born wolf born e wolf ''principle optics'' cambridge cambridge university press ref huygens fresnel equation one model derived empirically fresnel based huygens' hypothesis point wavefront generates secondary spherical wavefront fresnel


combined principle superposition waves kirchhoff diffraction equation derived using maxwell 's equations puts huygens fresnel equation firmer physical foundation examples application huygens fresnel principle found articles diffraction fraunhofer diffraction rigorous models involving modelling electric magnetic fields light wave required dealing materials whose electric magnetic properties affect interaction light material instance behaviour light wave interacting metal surface quite different happens


interacts dielectric material vector model must also used model polarised light numerical modeling techniques finite element method boundary element method transmission line matrix method used model propagation light systems cannot solved analytically models computationally demanding normally used solve small scale problems require accuracy beyond achieved analytical solutions results geometrical optics recovered using techniques fourier optics apply many mathematical


analytical techniques used acoustic engineering signal processing gaussian beam propagation simple paraxial physical optics model propagation coherent radiation laser beams technique partially accounts diffraction allowing accurate calculations rate laser beam expands distance minimum size beam focused gaussian beam propagation thus bridges gap geometric physical optics superposition interference absence nonlinear effects superposition principle used predict shape interacting waveforms simple addition


disturbances ref name interference interaction waves produce resulting pattern generally termed interference result variety outcomes two waves wavelength frequency ''in phase'' wave crests wave troughs align results constructive interference increase amplitude wave light associated brightening waveform location alternatively two waves wavelength frequency phase wave crests align wave troughs vice versa


results destructive interference decrease amplitude wave light associated dimming waveform location see illustration effect ref name interference chapter ref '''combined br waveform''' colspan rowspan file interference two wavessvg '''wave ''' '''wave ''' '''two waves phase''' '''two waves br phase''' oil fuel spilled colourful patterns formed thin film interference since huygens fresnel principle states every point wavefront associated production new disturbance


possible wavefront interfere constructively destructively different locations producing bright dark fringes regular predictable patterns ref name interference interferometry science measuring patterns usually means making precise determinations distances angular resolutions ref name interferometry ref michelson interferometer famous instrument used interference effects accurately measure speed light appearance thin films coatings directly affected interference effects antireflective coatings use destructive interference reduce reflectivity surfaces coat used minimise


glare unwanted reflections simplest case single layer thickness one fourth wavelength incident light reflected wave top film reflected wave film material interface exactly phase causing destructive interference waves exactly phase one wavelength would typically chosen near centre visible spectrum around nbsp nm complex designs using multiple layers achieve low reflectivity broad band extremely low reflectivity single wavelength constructive interference


separated angle math theta math numbered order math n math diffraction process light interference commonly observed effect first described francesco maria grimaldi also coined term latin ' 'diffringere'' 'to break pieces' later century robert hooke isaac newton also described phenomena known diffraction newton 's rings james gregory recorded observations diffraction patterns bird feathers first physical optics model diffraction relied huygens fresnel principle developed thomas young interference


experiments interference patterns two closely spaced slits young showed results could explained two slits acted two unique sources waves rather corpuscles augustin jean fresnel firmly established mathematics wave interference account diffraction ref name hecht simplest physical models diffraction use equations describe angular separation light dark fringes due light particular wavelength general equation takes form math lambda sin theta math math math separation two wavefront


atoms crystal regular spacing distances order one angstrom see diffraction patterns x rays similar wavelengths spacing passed crystal since crystals three dimensional objects rather two dimensional gratings associated diffraction pattern varies two directions according bragg reflection associated bright spots occurring unique patterns math math twice spacing atoms ref name diffraction diffraction effects limit ability optical detector optically resolve separate light sources general light passing aperture experience


two points cannot resolved image angular separation much greater distinct images two points formed therefore resolved rayleigh defined somewhat arbitrary rayleigh criterion two points whose angular separation equal airy disk radius measured first null first place light seen considered resolved seen greater diameter lens aperture finer resolution ref name diffraction interferometry ability


mimic extremely large baseline apertures allows greatest angular resolution possible ref name interferometry astronomical imaging atmosphere prevents optimal resolution achieved visible spectrum due atmospheric scattering dispersion cause stars twinkle astronomers refer effect quality astronomical seeing techniques known adaptive optics used eliminate atmospheric disruption images achieve results approach diffraction limit dispersion scattering conceptual animation light dispersion prism high frequency blue light deflected low frequency red


least refractive processes take place physical optics limit wavelength light similar distances kind scattering simplest type scattering thomson scattering occurs electromagnetic waves deflected single particles limit thomson scattering wavelike nature light evident light dispersed independent frequency contrast compton scattering frequency dependent strictly quantum mechanical process involving nature light particles statistical sense elastic scattering light numerous particles much smaller


wavelength light process known rayleigh scattering similar process scattering particles similar larger wavelength known mie scattering tyndall effect commonly observed result small proportion light scattering atoms molecules may undergo raman scattering wherein frequency changes due excitation atoms molecules brillouin scattering occurs frequency light changes due local changes time movements dense material dispersion occurs different frequencies light different phase velocities due


either material properties ''material dispersion'' geometry optical waveguide ''waveguide dispersion'' familiar form dispersion decrease index refraction increasing wavelength seen transparent materials called normal dispersion occurs dielectric materials wavelength ranges material absorb light ref name j ref wavelength ranges medium significant absorption index refraction increase wavelength called anomalous dispersion ref name geoptics ref name j separation colours prism example normal dispersion


surfaces prism snell 's law predicts light incident angle normal refracted angle arcsin sin ''n'' thus blue light higher refractive index bent strongly red light resulting well known rainbow pattern ref name geoptics dispersion two sinusoids propagating different speeds make moving interference pattern red dot moves phase velocity green dots propagate group velocity case phase velocity twice group velocity red dot overtakes two green dots moving


dispersion manifests spreading signal envelope radiation quantified group dispersion delay parameter math frac v g frac dv g lambda math math v g math group velocity ref name optnet ref uniform medium group velocity math v g c left n lambda frac dn lambda right math ''n'' index refraction ''c'' speed light vacuum gives simpler form dispersion delay parameter math frac lambda c frac n lambda math ''d'' less zero medium said ''positive dispersion''


normal dispersion ''d'' greater zero medium ''negative dispersion'' light pulse propagated normally dispersive medium result higher frequency components slow lower frequency components pulse therefore becomes ''positively chirped'' ''up chirped'' increasing frequency time causes spectrum coming prism appear red light least refracted blue violet light refracted conversely pulse travels anomalously negatively dispersive medium high frequency components travel faster lower ones pulse becomes ''negatively chirped''


' 'down chirped'' decreasing frequency time result group velocity dispersion whether negative positive ultimately temporal spreading pulse makes dispersion management extremely important optical communications systems based optical fibres since dispersion high group pulses representing information spread time merge making impossible extract signal ref name optnet polarization polarization general property waves describes orientation oscillations transverse waves many electromagnetic waves describes orientation oscillations plane perpendicular


components labeled ''x'' ''y'' '''z''' indicating direction travel shape traced x plane electric field vector lissajous figure describes ''polarization state'' ref name hecht following figures show examples evolution electric field vector blue time vertical axes particular point space along ''x'' ''y'' components red left green right path traced vector plane purple evolution would occur looking electric field particular time evolving


point space along direction opposite propagation div style float left width px linear polarization diagram center ''linear'' center div div style float left width px circular polarization diagram center ''circular'' center div div style float left width px elliptical polarization diagram center ''elliptical polarization'' center div leftmost figure x components light wave phase case ratio strengths constant direction electric vector vector sum two components constant since tip vector traces single line plane special case called linear polarization direction


line depends relative amplitudes two components ref name light middle figure two orthogonal components amplitudes phase case one component zero component maximum minimum amplitude two possible phase relationships satisfy requirement ''x'' component ahead ''y'' component behind ''y'' component special case electric vector traces circle plane polarization called circular polarization rotation


direction circle depends two phase relationships exists corresponds ''right hand circular polarization'' ''left hand circular polarization'' ref name hecht cases two components either amplitudes phase difference neither zero multiple polarization called elliptical polarization electric vector traces ellipse plane ''polarization ellipse'' shown figure right detailed mathematics polarization done using jones calculus characterised stokes parameters ref name hecht changing


polarization media different indexes refraction different polarization modes called ''birefringent'' ref name light well known manifestations effect appear optical wave plates retarders linear modes faraday rotation optical rotation circular modes ref name hecht path length birefringent medium sufficient plane waves exit material significantly different propagation direction due refraction example case macroscopic crystals calcite present viewer two offset orthogonally polarised images whatever viewed effect provided first discovery


polarization erasmus bartholinus addition phase shift thus change polarization state usually frequency dependent combination dichroism often gives rise bright colours rainbow like effects mineralogy properties known pleochroism frequently exploited purpose identifying minerals using polarization microscopes additionally many plastics normally birefringent become subject mechanical stress phenomenon basis photoelasticity ref name light non birefringent methods rotate linear polarization light beams include use prismatic polarization rotators


use total internal reflection prism set designed efficient collinear transmission polariser changing orientation linearly polarised light br picture '' '' sub sub '' sub sub '' '' sub sub '' media reduce amplitude certain polarization modes called ' 'dichroic'' devices block nearly radiation one mode known ''polarizing filters'' simply polarisers malus' law named tienne louis malus says perfect polariser placed linear polarised beam light intensity ''i'' light passes given math


cos theta quad math ''i'' sub sub initial intensity '' sub sub '' angle light 's initial polarization direction axis polariser ref name light beam unpolarised light thought containing uniform mixture linear polarizations possible angles since average value math cos theta math transmission coefficient becomes math frac frac quad math practice light lost polariser actual transmission unpolarised light somewhat lower around polaroid type polarisers considerably higher


birefringent prism types ref name hecht addition birefringence dichroism extended media polarization effects also occur reflective interface two materials different refractive index effects treated fresnel equations part wave transmitted part reflected ratio depending angle incidence angle refraction way physical optics recovers brewster 's angle ref name hecht light reflects thin film surface interference reflections film 's surfaces produce polarization reflected transmitted


light natural light polarising filter sky photograph left picture taken without polariser right picture filter adjusted eliminate certain polarizations scattered blue light sky sources electromagnetic radiation contain large number atoms molecules emit light orientation electric fields produced emitters may correlated case light said ''unpolarised'' partial correlation emitters light ''partially polarised'' polarization consistent across spectrum source


partially polarised light described superposition completely unpolarised component completely polarised one one may describe light terms degree polarization parameters polarization ellipse ref name hecht light reflected shiny transparent materials partly fully polarised except light normal perpendicular surface effect allowed mathematician tienne louis malus make measurements allowed development first mathematical models polarised light polarization occurs light scattered atmosphere scattered


light produces brightness colour clear skies partial polarization scattered light taken advantage using polarizing filters darken sky photographs optical polarization principally importance chemistry due circular dichroism optical rotation ''circular birefringence'' exhibited optically active chiral molecules ref name hecht modern optics ''modern optics'' encompasses areas optical science engineering became popular th century areas optical science typically relate electromagnetic quantum properties light include topics major subfield modern optics quantum


optics deals specifically quantum mechanical properties light quantum optics theoretical modern devices lasers principles operation depend quantum mechanics light detectors photomultipliers channeltrons respond individual photons electronic image sensors ccds exhibit shot noise corresponding statistics individual photon events light emitting diodes photovoltaic cells cannot understood without quantum mechanics study devices quantum optics often overlaps quantum electronics specialty areas optics research include study light interacts specific materials


crystal optics metamaterials research focuses phenomenology electromagnetic waves singular optics non imaging optics non linear optics statistical optics radiometry additionally computer engineers taken interest integrated optics machine vision photonic computing possible components next generation computers today pure science optics called optical science optical physics distinguish applied optical sciences referred optical engineering prominent subfields optical engineering include illumination engineering photonics optoelectronics practical applications like lens design fabrication testing optical components


image processing fields overlap nebulous boundaries subjects' terms mean slightly different things different parts world different areas industry professional community researchers nonlinear optics developed last several decades due advances laser technology lasers experiments one high power lasers part modern optics research laser device emits light kind electromagnetic radiation process called ' 'stimulated emission'' term ''laser'' acronym ''light amplification stimulated emission


radiation'' laser light usually spatially coherent means light either emitted narrow low divergence beam converted one help optical components lenses microwave equivalent laser ''maser'' developed first devices emit microwave radio frequencies usually called ''masers'' vlt 's laser guide star first working laser demonstrated may theodore maiman hughes research laboratories first invented called solution looking problem since lasers become multibillion dollar industry finding


utility thousands highly varied applications first application lasers visible daily lives general population supermarket barcode scanner introduced laserdisc player introduced first successful consumer product include laser compact disc player first laser equipped device become truly common consumers' homes beginning ref name bbc ref optical storage devices use semiconductor laser less millimetre wide scan surface disc data retrieval fibre optic communication relies lasers transmit large amounts information


speed light common applications lasers include laser printers laser pointers lasers used medicine areas bloodless surgery laser eye surgery laser capture microdissection military applications missile defence systems electro optical countermeasures eocm lidar lasers also used holograms bubblegrams laser light shows laser hair removal kapitsa dirac effect kapitsa dirac effect causes beams particles diffract result meeting standing wave light light used position matter using various phenomena see optical tweezers applications optics part


everyday life ubiquity visual systems biology indicates central role optics plays science one five senses many people benefit eyeglasses contact lenses optics integral functioning many consumer goods including cameras rainbows mirages examples optical phenomena optical communication provides backbone internet modern telephony human eye model human eye features mentioned article vitreous humour ciliary muscle pupil anterior chamber cornea lens cortex optic nerve fovea


fluid eye vitreous humour reaches retina cells retina line back eye except optic nerve exits results blind spot two types photoreceptor cells rods cones sensitive different aspects light ref name eyeoptics ref rod cells sensitive intensity light wide frequency range thus responsible black white vision rod cells present fovea area retina responsible central vision responsive cone cells spatial


rod cells since cone cells sensitive dim light rod cells night vision limited rod cells likewise since cone cells fovea central vision including vision needed reading fine detail work sewing careful examination objects done cone cells ref name kandel ciliary muscles around lens allow eye 's focus adjusted process known accommodation near point far point define nearest farthest distances eye object brought


sharp focus person normal vision far point located infinity near point 's location depends much muscles increase curvature lens inflexible lens become age optometrists ophthalmologists opticians usually consider appropriate near point closer normal reading distance approximately nbsp cm ref name eyeoptics defects vision explained using optical principles people age lens becomes less flexible near point recedes eye condition known presbyopia similarly people suffering hyperopia cannot decrease focal


length lens enough allow nearby objects imaged retina conversely people cannot increase focal length lens enough allow distant objects imaged retina suffer myopia far point considerably closer infinity condition known astigmatism results cornea spherical instead curved one direction causes horizontally extended objects focused different parts retina vertically extended objects results distorted images ref name eyeoptics


conditions corrected using corrective lenses presbyopia hyperopia converging lens provides extra curvature necessary bring near point closer eye myopia diverging lens provides curvature necessary send far point infinity astigmatism corrected cylindrical surface lens curves strongly one direction another compensating non uniformity cornea ref name lensdesign ref optical power corrective lenses measured diopters value equal reciprocal focal length measured metres positive focal length


corresponding converging lens negative focal length corresponding diverging lens lenses correct astigmatism well three numbers given one spherical power one cylindrical power one angle orientation astigmatism ref name lensdesign visual effects ponzo illusion relies fact parallel lines appear converge approach infinity optical illusions also called visual illusions characterized visually perceived images differ objective reality information gathered eye processed brain give percept


diverging lines way parallel light rays indeed set parallel lines appear converge vanishing point infinity two dimensionally rendered images artistic perspective suggestion also responsible famous moon illusion moon despite essentially angular size appears much larger near horizon zenith illusion confounded ptolemy incorrectly attributed atmospheric refraction described treatise ''optics'' ref name ptolemy another type optical illusion exploits broken patterns trick mind


perceiving symmetries asymmetries present examples include caf wall ehrenstein fraser spiral poggendorff z llner illusions related strictly illusions patterns occur due superimposition periodic structures example transparent tissues grid structure produce shapes known moir patterns superimposition periodic transparent patterns comprising parallel opaque lines curves produces line moir patterns optical instruments cyclopaedia'' single lenses variety applications including photographic lenses corrective lenses magnifying glasses single mirrors used parabolic reflectors rear view mirrors combining number


mirrors prisms lenses produces compound optical instruments practical uses example periscope simply two plane mirrors aligned allow viewing around obstructions famous compound optical instruments science microscope telescope invented dutch late th century ref name instrument ref microscopes first developed two lenses objective lens eyepiece objective lens essentially magnifying glass designed small focal length eyepiece generally longer focal length effect


producing magnified images close objects generally additional source illumination used since magnified images dimmer due conservation energy spreading light rays larger surface area modern microscopes known ''compound microscopes'' many lenses typically four optimize functionality enhance image stability ref name instrument slightly different variety microscope comparison microscope looks side side images produce stereoscopic binocular view appears three dimensional used humans first telescopes called refracting telescopes also developed single objective


changed switching eyepieces magnification telescope equal focal length objective divided focal length eyepiece smaller focal length eyepieces cause greater magnification ref name instrument since crafting large lenses much difficult crafting large mirrors modern telescopes ' 'reflecting telescopes'' telescopes use primary mirror rather objective lens general optical considerations apply reflecting telescopes applied refracting telescopes namely larger primary mirror light collected magnification still equal


words smaller aperture giving greater depth focus less light coming length time increased leading possible blurriness motion occurs example use law reciprocity sunny rule gives rough estimate settings needed estimate proper exposure daylight camera 's aperture measured unitless number called f number f stop often notated math n math given math f n frac fd math math f math focal length math math


view wider focal length shorter normal lens long focus lens angle view narrower normal lens lens focal length longer diagonal measure film sensor common type long focus lens telephoto lens design uses special ''telephoto group'' physically shorter focal length modern zoom lenses may attributes absolute value exposure time required depends sensitive light medium used


measured film speed digital media quantum efficiency early photography used media low light sensitivity exposure times long even bright shots technology improved sensitivity film cameras digital cameras results physical geometrical optics apply camera optics example maximum resolution capability particular camera set determined diffraction limit associated pupil size given roughly rayleigh criterion atmospheric optics colourful sky often due scattering


light particulates pollution photograph sunset october california wildfires unique optical properties atmosphere cause wide range spectacular optical phenomena blue colour sky direct result rayleigh scattering redirects higher frequency blue sunlight back field view observer blue light scattered easily red light sun takes reddish hue observed thick atmosphere sunrise sunset additional particulate matter sky


scatter different colours different angles creating colourful glowing skies dusk dawn scattering ice crystals particles atmosphere responsible halos afterglows coronas rays sunlight sun dogs variation kinds phenomena due different particle sizes geometries ref name autogenerated ref mirages optical phenomena light rays bent due thermal variations refraction index air producing displaced heavily distorted images distant objects dramatic optical phenomena associated include novaya zemlya effect sun appears rise


earlier predicted distorted shape spectacular form refraction occurs temperature inversion called fata morgana objects horizon even beyond horizon islands cliffs ships icebergs appear elongated elevated like fairy tale castles rainbows result combination internal reflection dispersive refraction light raindrops single reflection backs array raindrops produces rainbow angular size sky ranges red outside double rainbows produced


two internal reflections angular size violet outside rainbows seen sun away centre rainbow rainbows prominent closer sun horizon ref name light see also ion optics important publications optics list optical topics references reading external links relevant discussions textbooks tutorials http lightandmattercom lm light matter open source textbook containing treatment optics ch http wwwoptics com optics optics library community https webarchiveorg web http marketplaceidexopcom store supportdocuments fundamental optics overviewwebpdf fundamental optics melles griot technical guide http opticsbyuedu textbookaspx physics


light optics brigham young university undergraduate book https wwwpvlighthousecomau cms lectures altermatt optics optics pv step step introduction classical optics wikibooks modules physics study guide optics optics reading http wwwioporg publications iop page html optics photonics physics enhancing lives http wwwioporg publications iop indexhtml institute physics publications societies european optical society http wwwmyeosorg link optical society osa http wwwosaorg link spie http wwwspieorg link european photonics industry consortium http wwwepic assoccom link electromagnetic radiation applied interdisciplinary physics natural philosophy


'''ordering points identify clustering structure''' '''optics''' algorithm finding density based clusters spatial data presented mihael ankerst markus breunig hans peter kriegel j rg sander ref name ref basic idea similar dbscan addresses one dbscan 's major weaknesses problem detecting meaningful clusters data varying density points database linearly ordered spatially closest points become neighbors ordering additionally special distance stored point represents density must accepted


cluster points belong cluster represented dendrogram basic idea like dbscan optics requires two parameters describes maximum distance radius consider describing number points required form cluster point ''core point'' least points found within neighborhood math n varepsilon p math including point contrast dbscan optics also considers points part densely packed cluster point assigned ''core distance'' describes distance th closest


point math text core dist mathit varepsilonminpts p begin cases text undefined text n varepsilon p mathit minpts mathit minpts text th smallest distance n varepsilon p text otherwise end cases math ' 'reachability distance'' another point point either distance core distance whichever bigger math text reachability dist mathit varepsilonminpts op begin cases text undefined text n varepsilon p mathit minpts max text core dist mathit varepsilonminpts p text dist po text otherwise end cases math nearest neighbors math varepsilon' varepsilon math need assume belong cluster core distance reachability distance undefined sufficiently dense cluster wrt


give maximum value pseudocode basic approach optics similar dbscan instead maintaining known far unprocessed cluster members set maintained priority queue eg using indexed heap '''function''' optics db eps minpts '''is''' '''for each''' point p db '' 'do''' preachability distance undefined '''for each''' unprocessed point p db '' 'do''' n getneighbors p eps mark p processed output p ordered list '''if''' core distance p eps minpts undefined '''then''' seeds empty priority queue update n p seeds eps minpts '''for each''' next q seeds


'' 'do''' n' getneighbors q eps mark q processed output q ordered list '''if''' core distance q eps minpts undefined '' 'do''' update n' q seeds eps minpts update priority queue seeds updated math varepsilon math neighborhood math p math math q math respectively '''function''' update n p seeds eps minpts '''is''' coredist core distance p eps minpts '''for each''' n '''if''' processed '''then''' new reach dist max coredist dist po '''if''' oreachability distance undefined '''then''' seeds oreachability distance new reach dist seedsinsert new reach dist '''else'''


seeds check improvement '''if''' new reach dist oreachability distance '''then''' oreachability distance new reach dist seedsmove new reach dist optics hence outputs points particular ordering annotated smallest reachability distance original algorithm core distance also exported required processing extracting clusters file opticssvg using ' 'reachability plot'' special kind dendrogram hierarchical structure clusters obtained easily plot ordering points processed optics x axis reachability distance axis since points


belonging cluster low reachability distance nearest neighbor clusters show valleys reachability plot deeper valley denser cluster image illustrates concept upper left area synthetic example data set shown upper right part visualizes spanning tree produced optics lower part shows reachability plot computed optics colors plot labels computed algorithm well visible valleys plot correspond clusters


data set yellow points image considered noise valley found reachability plot usually assigned clusters except omnipresent data cluster hierarchical result extracting clusters plot done manually selecting range x axis visual inspection selecting threshold axis result similar dbscan clustering result math varepsilon math parameters value may yield good results different algorithms try detect valleys


outlier detection method better known version lof based concepts deli clu density link clustering combines ideas single linkage clustering optics eliminating math varepsilon math parameter offering performance improvements optics hisc hierarchical subspace clustering axis parallel method based optics hico hierarchical correlation clustering algorithm based optics dish improvement hisc find complex hierarchies foptics faster implementation using random projections hdbscan based refinement dbscan excluding border points clusters thus following strictly basic definition density levels hartigan availability


''n'' butyllithium organometallic compound four lithium atoms purple form tetrahedron four butyl groups attached faces carbon black hydrogen white '''organometallic chemistry''' study '''organometallic compounds''' chemical compounds containing least one chemical bond carbon atom organic molecule metal including alkaline alkaline earth transition metals sometimes broadened include metalloids like boron silicon selenium well ref name ref aside bonds organyl fragments molecules bonds 'inorganic' carbon like carbon monoxide metal carbonyls cyanide carbide generally considered

Natural science
Chemistry
Organometallic chemistry


role catalysts increase rates reactions eg uses homogeneous catalysis target molecules include polymers pharmaceuticals many types practical products organometallic compounds magnesium bis cyclopentadienyl hazardous substance like organometallics text states federal law forbids transportation refilled penalty fine year imprisonment organometallic compounds distinguished prefix organo eg organopalladium compounds include compounds contain bond metal atom carbon atom organyl group ref name addition traditional metals


alkali metals alkali earth metals transition metals post transition metals lanthanides actinides semimetals elements boron silicon arsenic selenium considered form organometallic compounds ref name examples organometallic compounds include gilman reagents contain lithium copper grignard reagents contain magnesium tetracarbonyl nickel ferrocene examples organometallic compounds containing transition metals examples organometallic compounds include organolithium compounds ''n'' butyllithium n buli organozinc compounds diethylzinc et sub sub zn organotin compounds tributyltin hydride bu sub sub snh organoborane compounds triethylborane et sub sub b organoaluminium compounds trimethylaluminium sub sub al naturally


occurring organometallic complex methylcobalamin form vitamin b sub sub contains cobalt methyl bond complex along biologically relevant complexes often discussed within subfield bioorganometallic chemistry gallery widths heights caption representative organometallic compounds file ferrocenesvg ferrocene archetypal organoiron complex air stable sublimable compound file cobaltocenesvg cobaltocene structural analogue ferrocene highly reactive toward air file hrh co p againpng tris triphenylphosphine rhodium carbonyl hydride used commercial production many aldehyde based fragrances file zeise 'ssaltpng zeise 's salt example transition metal alkene complex file trimethylaluminium xtal bs png trimethylaluminium organometallic compound bridging methyl group


used industrial production alcohols file dimethylzinc ballspng dimethylzinc linear coordination volatile pyrophoric liquid used preparation semiconducting films file lithium diphenylcuprate etherate dimer xtal skeletalpng lithium diphenylcuprate bis diethyl etherate example gilman reagent type organocopper complex frequently employed organic synthesis file adocbl colorcodedpng adenosylcobalamin cofactor required several crucial enzymatic reactions take place human body rare example metal cobalt alkyl biology file ironpentacarbonylstructurepng iron pentacarbonyl red orange liquid prepared directly union finely divided iron carbon monoxide gas


pressure file tc sestamibi structuresvg technetium sup sup tc sestamibi used image heart muscle nuclear medicine gallery distinction coordination compounds organic ligands many complexes feature coordination bonds metal organic ligands complexes organic ligands bind metal heteroatom oxygen nitrogen considered coordination compounds eg heme fe acac sub sub however ligands form direct metal carbon c bond complex considered organometallic although iupac formally defined term chemists use term metalorganic describe coordination compound


zn zn c bonds organometallic nature structure properties metal carbon bond organometallic compounds generally highly covalent highly electropositive elements lithium sodium carbon ligand exhibits carbanionic character free carbon based anions extremely rare example cyanide organometallic compounds solids room temperature however liquids methylcyclopentadienyl manganese tricarbonyl even volatile liquids nickel tetracarbonyl many organometallic compounds air sensitive reactive towards oxygen moisture thus must handled inert atmosphere organometallic compounds


triethylaluminium pyrophoric ignite contact air concepts techniques areas chemistry electron counting useful organizing organometallic chemistry electron rule helpful predicting stabilities organometallic complexes example metal carbonyls metal hydrides however many organometallic compounds follow e rule metal atoms organometallic compounds frequently described electron count oxidation state concepts used help predict reactivity preferred geometry chemical bonding reactivity organometallic compounds often discussed perspective


isolobal principle wide variety physical techniques used determine structure composition properties organometallic compounds x ray diffraction particularly important technique locate positions atoms within solid compound providing detailed description structure techniques like infrared spectroscopy nuclear magnetic resonance spectroscopy also frequently used obtain information structure bonding organometallic compounds ultraviolet visible spectroscopy common technique used obtain information electronic structure organometallic compounds also used monitor progress organometallic reactions well


mond 's discovery ni co sub sub victor grignard 's organomagnesium compounds though always acknowledged organometallic compound prussian blue mixed valence iron cyanide complex first prepared paint maker johann jacob diesbach first coordination polymer synthetic material containing metal carbon bond abundant diverse products coal petroleum led ziegler natta fischer tropsch hydroformylation catalysis employ co h sub sub alkenes feedstocks ligands recognition organometallic chemistry distinct subfield culminated nobel prizes ernst fischer geoffrey wilkinson work metallocenes yves chauvin robert


h grubbs richard r schrock shared nobel prize metal catalyzed olefin metathesis organometallic chemistry timeline louis claude cadet de gassicourt investigates inks based cobalt salts isolates cacodyl cobalt mineral containing arsenic william christopher zeise produces zeise 's salt first platinum olefin complex edward frankland discovers diethylzinc charles friedel james crafts prepare organochlorosilanes ludwig mond discovers nickel carbonyl introduction grignard reaction john ulric nef discovers alkynylation using sodium acetylides paul sabatier works hydrogenation organic compounds metal catalysts hydrogenation fats kicks


advances food industry see margarine paul ehrlich introduces salvarsan treatment syphilis early arsenic based organometallic compound nobel prize victor grignard paul sabatier henry gilman works lithium cuprates see gilman reagent walter hieber awarded alfred stock prize work metal carbonyl chemistry ferrocene discovered dorothy crawfoot hodgkin determines structure vitamin b sub sub first biomolecule found contain metal carbon bond see bioorganometallic chemistry nobel prize karl ziegler giulio natta ziegler natta catalyst discovery cyclobutadieneiron tricarbonyl


heck reaction developed nobel prize geoffrey wilkinson ernst otto fischer sandwich compounds nobel prize roald hoffmann kenichi fukui creation woodward hoffman rules nobel prize w knowles r noyori karl barry sharpless asymmetric hydrogenation nobel prize yves chauvin robert grubbs richard schrock metal catalyzed alkene metathesis nobel prize richard f heck ei ichi negishi akira suzuki palladium catalyzed cross coupling reactions scope subspecialty areas organometallic chemistry include period elements organolithium chemistry organoberyllium chemistry organoborane chemistry period elements organosodium chemistry organomagnesium chemistry organoaluminium


chemistry organosilicon chemistry period elements organocalcium chemistry organoscandium chemistry organotitanium chemistry organovanadium chemistry organochromium chemistry organomanganese chemistry organoiron chemistry organocobalt chemistry organonickel chemistry organocopper chemistry organozinc chemistry organogallium chemistry organogermanium chemistry organoarsenic chemistry organoselenium chemistry period elements organoyttrium chemistry organozirconium chemistry organoniobium chemistry organomolybdenum chemistry organoruthenium chemistry organorhodium chemistry organopalladium chemistry organosilver chemistry organocadmium chemistry organoindium chemistry organotin chemistry organoantimony chemistry organotellurium chemistry period elements organolanthanide chemistry organocerium chemistry organotantalum chemistry organorhenium chemistry organoosmium chemistry organoiridium chemistry organoplatinum chemistry organogold chemistry organomercury chemistry organothallium chemistry organolead chemistry organobismuth chemistry organopolonium chemistry period elements organoactinide chemistry


organouranium chemistry organoneptunium chemistry industrial applications organometallic compounds find wide use commercial reactions homogenous catalysts stoichiometric reagents instance organolithium organomagnesium organoaluminium compounds examples highly basic highly reducing useful stoichiometrically also catalyze many polymerization reactions almost processes involving carbon monoxide rely catalysts notable examples described carbonylations ref name ullmann ref production acetic acid methanol carbon monoxide catalyzed via metal carbonyl complexes monsanto process cativa process synthetic aldehydes produced via hydroformylation bulk


synthetic alcohols least larger ethanol produced hydrogenation hydroformylation derived aldehydes similarly wacker process used oxidation ethylene acetaldehyde constrained geometry organotitanium complex precatalyst olefin polymerization almost industrial processes involving alkene derived polymers rely organometallic catalysts world 's polyethylene polypropylene produced via heterogeneously via ziegler natta catalysis homogeneously eg via constrained geometry catalysts processes involving hydrogen rely metal based catalysts whereas bulk hydrogenations eg margarine production rely heterogeneous catalysts production fine chemicals hydrogenations rely


molecules facilitated organometallic complexes sigma bond metathesis synthetic method forming new carbon carbon sigma bonds sigma bond metathesis typically used early transition metal complexes highest oxidation state using transition metals highest oxidation state prevents reactions occurring oxidative addition addition sigma bond metathesis olefin metathesis used synthesize various carbon carbon pi bonds neither sigma bond metathesis olefin metathesis change oxidation state metal many methods used form new carbon carbon bonds including beta hydride elimination insertion reactions catalysis organometallic


complexes commonly used catalysis major industrial processes include hydrogenation hydrosilylation hydrocyanation olefin metathesis alkene polymerization alkene oligomerization hydrocarboxylation methanol carbonylation hydroformylation organometallic intermediates also invoked many heterogeneous catalysis processes analogous listed additionally organometallic intermediates assumed fischer tropsch process organometallic complexes commonly used small scale fine chemical synthesis well especially cross coupling reactions form carbon carbon bonds eg suzuki miyaura coupling buchwald hartwig amination producing aryl amines aryl halides sonogashira coupling etc environmental concerns roxarsone organoarsenic compound used animal feed natural


contaminant organometallic compounds found environment remnants human use organolead organomercury compounds toxicity hazards tetraethyllead prepared use gasoline additive fallen disuse lead 's toxicity replacements organometallic compounds ferrocene methylcyclopentadienyl manganese tricarbonyl mmt ref name seyferth ref organoarsenic compound roxarsone controversial animal feed additive approximately one million kilograms produced us alone organotin compounds widely used anti fouling paints since banned due environmental concerns


see also bioorganometallic chemistry metal carbon dioxide complex references sources external links https webarchiveorg web http ocwmitedu ocwweb chemistry fall coursehome indexhtm mit opencourseware organometallic chemistry http wwwilpicom organomet rob toreki 's organometallic hypertextbook http wwworganometallicsnet web listing us chemists specialize organometallic chemistry


''the school athens'' raphael depicting famous classical greek philosophers idealized setting inspired ancient greek architecture '''philosophy''' ref name online etymology dictionary ref name webster 's new world dictionary study general fundamental questions existence reason knowledge values mind language questions often posed problems studied resolved sources claim term coined pythagoras c c bce others dispute story arguing pythagoreans merely claimed use preexisting term philosophical methods include questioning critical discussion


rational argument systematic presentation ref name justification ref group lower roman quinton anthony ethics philosophical practice p ''the oxford companion philosophy'' edited honderich new york oxford university press philosophy rationally critical thinking less systematic kind general nature world metaphysics theory existence justification belief epistemology theory knowledge conduct life ethics theory value three elements list non philosophical counterpart distinguished explicitly rational critical way


proceeding systematic nature everyone general conception nature world live place metaphysics replaces unargued assumptions embodied conception rational organized body beliefs world whole everyone occasion doubt question beliefs others less success without theory epistemology seeks argument make explicit rules correct belief formation everyone governs conduct directing


desired valued ends ethics moral philosophy inclusive sense seeks articulate rationally systematic form rules principles involved p ref historically ''philosophy'' encompassed bodies knowledge practitioner known ''philosopher'' ref name english word philosophy first attested c meaning knowledge body knowledge harper douglas https wwwetymonlinecom searchq philosophy philosophy n ''online etymology dictionary'' retrieved may ref time ancient greek philosopher aristotle th century natural philosophy encompassed astronomy medicine physics example newton 's ''mathematical principles natural philosophy'' later


allow one derive conclusions true premises notable subfields include philosophy science political philosophy aesthetics philosophy language philosophy mind definitions initially term referred body knowledge ref name sense philosophy closely related religion mathematics natural science education politics section thirteen ''lives opinions eminent philosophers'' oldest surviving history philosophy rd century diogenes la rtius presents three part division ancient greek philosophical inquiry natural philosophy ie physics study constitution processes transformation


physical world moral philosophy ie ethics study goodness right wrong justice virtue metaphysical philosophy ie logic study existence causation god logic forms abstract objects ''against logicians'' pyrrhonist philosopher sextus empiricus detailed variety ways ancient greek philosophers divided philosophy noting three part division agreed plato aristotle xenocrates stoics academic skeptic philosopher cicero also followed three part division division obsolete changed ''natural philosophy''


split various natural sciences especially physics astronomy chemistry biology cosmology ''moral philosophy'' birthed social sciences still including value theory eg ethics aesthetics political philosophy etc ''metaphysical philosophy'' given way formal sciences logic mathematics philosophy science still including epistemology cosmology etc example newton 's ''mathematical principles natural philosophy'' since classified book physics uses term ''natural philosophy'' understood time encompassing disciplines astronomy medicine physics later became associated sciences historical overview


pre socratic thinkers active th century greece bce thales bce pythagoras bce practiced 'love wisdom' ref name title lectures history philosophy greek philosophy last brown first robert f date publisher clarendon press isbn page ref also termed 'students nature' western philosophy divided three eras ref name auto ref ancient greco roman ref name auto medieval philosophy referring christian european thought ref name auto modern philosophy beginning th century ref name auto ancient era knowledge ancient era begins thales th century bce little known


philosophers came socrates commonly known pre socratics ancient era dominated greek philosophical schools notable among schools influenced socrates' teachings plato founded platonic academy student aristotle ref name process founded peripatetic school ancient philosophical traditions influenced socrates included cynicism cyrenaicism stoicism academic skepticism two traditions influenced socrates' contemporary democritus pyrrhonism epicureanism important topics covered greeks included metaphysics competing theories atomism monism cosmology nature well lived life ''eudaimonia'' possibility


knowledge nature reason logos rise roman empire greek philosophy increasingly discussed latin romans cicero seneca see roman philosophy medieval era medieval philosophy th th centuries period following fall western roman empire dominated rise christianity hence reflects judeo christian theological concerns well retaining continuity greco roman thought problems existence nature god nature faith reason metaphysics problem evil discussed period


key medieval thinkers include st augustine thomas aquinas boethius anselm roger bacon philosophy thinkers viewed aid theology hence sought align philosophy interpretation sacred scripture period saw development scholasticism text critical method developed medieval universities based close reading disputation key texts renaissance period saw increasing focus classic greco roman thought robust humanism modern era painting influential modern philosopher immanuel kant blue coat friends figures


include christian jakob kraus johann georg hamann theodor gottlieb von hippel karl gottfried hagen early modern philosophy western world begins thinkers thomas hobbes ren descartes ref name diane ref following rise natural science modern philosophy concerned developing secular rational foundation knowledge moved away traditional structures authority religion scholastic thought church major modern philosophers include spinoza leibniz locke berkeley hume kant th century philosophy sometimes called late modern philosophy influenced wider th century movement termed enlightenment includes figures


mostly dominated islamic culture according assyriologist marc van de mieroop babylonian philosophy highly developed system thought unique approach knowledge focus writing lexicography divination law also bilingual intellectual culture based sumerian akkadian vizier ptahhotep c bce early wisdom literature fertile crescent genre sought instruct people ethical action practical living virtue stories proverbs ancient egypt texts known ' 'sebayt'' 'teachings' central understandings ancient egyptian


philosophy well known texts ''the maxims ptahhotep'' theology cosmology central concern egyptian thought perhaps earliest form monotheistic theology also emerged egypt rise amarna theology atenism akhenaten th century bce held solar creation deity aten god described monotheistic revolution egyptologist jan assmann though also drew previous developments egyptian thought particularly new solar theology based around amun ra ref name assmann jan '' http archivubuni heidelbergde propylaeumdok assmann theological responses amarna pdf theological responses amarna '' originalver ffentlichung


gary n knoppers antoine hirsch hg egypt israel ancient mediterranean world studies honor donald b redford leiden boston ref theological developments also influenced post amarna ramesside theology retained focus single creative solar deity though without outright rejection gods seen manifestations main solar deity period also saw development concept ''ba'' soul relation god ref name jewish philosophy christian philosophy religious philosophical traditions developed middle east europe


share certain early judaic texts mainly tanakh monotheistic beliefs jewish thinkers geonim talmudic academies babylonia maimonides engaged greek islamic philosophy later jewish philosophy came strong western intellectual influences includes works moses mendelssohn ushered haskalah jewish enlightenment jewish existentialism reform judaism various traditions gnosticism influenced greek abrahamic currents originated around first century emphasized spiritual knowledge ''gnosis'' pre islamic iranian philosophy begins work zoroaster one first promoters monotheism


arabic early islamic philosophy developed greek philosophical traditions new innovative directions intellectual work inaugurated known islamic golden age two main currents early islamic thought kalam focuses islamic theology falsafa based aristotelianism neoplatonism work aristotle influential among philosophers al kindi th century avicenna june averroes th century others al ghazali highly critical methods islamic aristotelians saw metaphysical ideas heretical islamic thinkers like ibn al haytham al biruni


also developed scientific method experimental medicine theory optics legal philosophy ibn khaldun influential thinker philosophy history islamic thought also deeply influenced european intellectual developments especially commentaries averroes aristotle mongol invasions destruction baghdad often seen marking end golden age several schools islamic philosophy continued flourish golden age however include currents illuminationist philosophy sufi philosophy transcendent theosophy th th century arab world saw ''nahda'' movement literally meaning 'the


awakening' also known 'arab renaissance' considerable influence contemporary islamic philosophy eastern philosophy indian philosophy adi shankara one frequently studied hindu philosophers indian philosophy lit point view' 'perspective refers diverse philosophical traditions emerged since ancient times indian subcontinent indian philosophical traditions share various key concepts ideas defined different ways accepted rejected different traditions include concepts ' 'dh rma'' ''karma'' ''pram a'' ' 'du kha sa ra'' ''mok a'' earliest surviving indian philosophical texts


upanishads later vedic period bce considered preserve ideas brahmanism indian philosophy commonly grouped based relationship vedas ideas contained jainism buddhism originated end vedic period various traditions grouped hinduism mostly emerged vedic period independent traditions hindus generally classify indian philosophical traditions either orthodox '' stika'' heterodox ''n stika'' depending whether accept authority vedas theories ''brahman'' '' tman'' found therein schools align


thought upanishads called orthodox hindu traditions often classified six ' 'dar anas'' philosophies nkhya yoga ny ya vaisheshika mim ms ved nta doctrines vedas upanishads interpreted differently six schools hindu philosophy varying degrees overlap represent collection philosophical views share textual connection according chadha also reflect tolerance diversity philosophical interpretations within hinduism sharing foundation ref name sharma p group lower roman attitude towards existence god varies within hindu religious tradition may


entirely unexpected given tolerance doctrinal diversity tradition known thus six orthodox systems hindu philosophy three address question detail schools thought known nyaya yoga theistic forms vedanta pp ref hindu philosophers six orthodox schools developed systems epistemology ''pramana'' investigated topics metaphysics ethics psychology ''gu a'' hermeneutics soteriology within framework vedic knowledge presenting diverse collection interpretations ref name frazierintrop ref commonly named six orthodox schools competing philosophical


traditions called hindu synthesis classical hinduism also schools thought often seen hindu though necessarily orthodox since may accept different scriptures normative shaiva agamas tantras include different schools shavism pashupata shaiva siddhanta non dual tantric shavism ie trika kaula etc k ntav da hindu orthodox traditions often contrasted unorthodox traditions ''n stika'' literally reject though label used unorthodox schools traditions reject vedas


authoritative often reject major concepts ideas widely accepted orthodox schools '' tman'' ''brahman'' '' vara'' ref name bilimoriaastika bilimoria p ''indian philosophy'' edited r perrett london routledge p ref unorthodox schools include jainism accepts '' tman'' rejects '' vara'' vedas ''brahman'' buddhism rejects orthodox concepts except rebirth karma c rv ka materialists reject even rebirth karma j vika known doctrine fate ref name bilimoriaastika ref name bhattacarv r bhattacharya studies carvaka lokayata anthem pp ref ref name bronkhorst johannes bronkhorst free indian philosophy antiquorum philosophia international


journal roma italy volume pp ref ref group lower roman wynne alexander tman negation ''journal international association buddhist studies'' denial human possesses self soul probably famous buddhist teaching certainly distinct pointed gp malalasekera 'in denial real permanent soul self buddhism stands alone' similar modern sinhalese perspective expressed walpola rahula 'buddhism stands unique history human thought denying existence soul self tman'


'no self' 'no soul' doctrine particularly notable widespread acceptance historical endurance standard belief virtually ancient schools indian buddhism notable exception pudgalav dins persisted without change modern era b oth views mirrored modern therav din perspective mahasi sayadaw 'there person soul' modern mah na view fourteenth dalai lama ' buddha taught belief independent self root cause suffering' ref jain philosophy one


two surviving unorthodox traditions along buddhism generally accepts concept permanent soul ''jiva'' one five ''astikayas'' eternal infinite categories make substance existence four ' 'dh rma'' ''adharma'' '' k a'' 'space' ''pudgala'' 'matter' jain thought holds existence cyclic eternal uncreated important elements jain philosophy jain theory karma doctrine nonviolence ahi theory many sidedness k ntav da ''tattvartha sutra'' earliest known comprehensive authoritative compilation jain philosophy buddhist


philosophy monks debating sera monastery tibet according jan westerhoff public debates constituted important visible forms philosophical exchange ancient indian intellectual life buddhist philosophy begins thought gautama buddha fl th th century bce preserved early buddhist texts originated indian region magadha later spread rest indian subcontinent east asia tibet central asia southeast asia regions buddhist thought developed different philosophical traditions used various languages like tibetan chinese pali


buddhist philosophy trans cultural international phenomenon dominant buddhist philosophical traditions east asian nations mainly based indian mahayana buddhism philosophy theravada school dominant southeast asian countries like sri lanka burma thailand ignorance true nature things considered one roots suffering ' 'dukkha'' buddhist philosophy concerned epistemology metaphysics ethics psychology buddhist philosophical texts must also understood within context meditative practices supposed bring certain cognitive shifts ref name westerhoff jan ''the golden age


indian buddhist philosophy'' oxford oxford university press ref key innovative concepts include four noble truths analysis ' 'dukkha'' ''anicca'' impermanence ''anatta'' non self ref group lower roman phenomenal existence buddhism said three interlocking characteristics impermanence suffering lack soul essence p ref death buddha various groups began systematize main teachings eventually developing comprehensive philosophical systems termed ''abhidharma'' ref name following abhidharma schools indian mahayana philosophers nagarjuna vasubandhu developed theories '' nyat '' 'emptiness phenomena' ''vij apti matra'' 'appearance only' form phenomenology


transcendental idealism dign ga school ''pram a'' 'means knowledge' promoted sophisticated form buddhist epistemology numerous schools sub schools traditions buddhist philosophy ancient medieval india according oxford professor buddhist philosophy jan westerhoff major indian schools bce ce ref name mah ghika tradition extinct sthavira schools sarv stiv da vibhajyav da pudgalav da mahayana schools many traditions also studied regions like central asia china brought buddhist missionaries disappearance buddhism india


developments saw rise major philosophical schools china confucianism also known ruism legalism taoism well numerous less influential schools like mohism naturalism philosophical traditions developed metaphysical political ethical theories tao yin yang ren li schools thought developed han bce ce tang ce eras forming new philosophical movements like ''xuanxue'' also called ''neo taoism'' neo confucianism neo confucianism syncretic philosophy incorporated ideas different chinese philosophical traditions including buddhism taoism neo confucianism


came dominate education system song dynasty ideas served philosophical basis imperial exams scholar official class important neo confucian thinkers tang scholars han yu li ao well song thinkers zhou dunyi zhu xi zhu xi compiled confucian canon consists four books ''great learning'' ''doctrine mean'' ''analects'' confucius ''mencius'' ming scholar wang yangming later important philosopher tradition


imperial state japan tokugawa shogunate also strongly influenced confucian philosophy confucianism continues influence ideas worldview nations chinese cultural sphere today modern era chinese thinkers incorporated ideas western philosophy chinese marxist philosophy developed influence mao zedong chinese pragmatism developed hu shih old traditional philosophies also began reassert th century example new confucianism led figures xiong shili become quite influential likewise humanistic buddhism recent modernist buddhist movement modern japanese


thought meanwhile developed strong western influences study western sciences rangaku modernist meirokusha intellectual society drew european enlightenment thought promoted liberal reforms well western philosophies like liberalism utilitarianism another trend modern japanese philosophy national studies kokugaku tradition intellectual trend sought study promote ancient japanese thought culture kokugaku thinkers motoori norinaga sought return pure japanese tradition called shinto saw untainted foreign elements th century kyoto school influential


unique japanese philosophical school developed western phenomenology medieval japanese buddhist philosophy dogen african philosophy painting zera yacob claude sumner 's ''classical ethiopian philosophy'' african philosophy philosophy produced african people philosophy presents african worldviews ideas themes philosophy uses distinct african philosophical methods modern african thought occupied ethnophilosophy defining meaning african philosophy unique characteristics means african th century ethiopian philosophy developed robust literary tradition exemplified zera yacob


another early african philosopher anton wilhelm amo c became respected philosopher germany distinct african philosophical ideas include ujamaa bantu idea 'force' n gritude pan africanism ubuntu contemporary african thought also seen development professional philosophy africana philosophy philosophical literature african diaspora includes currents black existentialism african americans modern african thinkers influenced marxism african american literature critical theory critical race theory postcolonialism feminism indigenous american philosophy tlamatini aztec philosopher observing stars codex mendoza indigenous american philosophical


thought consists wide variety beliefs traditions among different american cultures among us native american communities belief metaphysical principle called 'great spirit' siouan ''wak ka'' algonquian ''gitche manitou'' another widely shared concept ''orenda'' 'spiritual power' according whiteley native americans mind critically informed transcendental experience dreams visions well reason ref name reproutledgecom whiteley peter https wwwreproutledgecom articles thematic native american philosophy v native american philosophy ''routledge encyclopedia philosophy'' taylor francis ref practices access transcendental experiences


social sciences vol march sage publications ref authors also poets work survived original nahuatl ref name ref name aztec philosophers developed theories metaphysics epistemology values aesthetics aztec ethics focused seeking ''tlamatiliztli'' 'knowledge' 'wisdom' based moderation balance actions nahua proverb middle good necessary ref name ieputmedu nahua worldview posited concept ultimate universal energy force called '' mete tl'' 'dual cosmic energy' sought way live balance


constantly changing slippery world theory ''teotl'' seen form pantheism ref name ieputmedu ref according james maffie nahua metaphysics posited teotl single vital dynamic vivifying eternally self generating self conceiving well self regenerating self reconceiving sacred energy force ref name force seen encompassing life force universe universe ref name depiction pachacuti worshipping inti god sun coricancha th century second chronicles mart n de mur pachacuti major incan ruler author poet inca civilization also


elite class philosopher scholars termed ''amawtakuna'' ''amautas'' important inca education system teachers philosophy theology astronomy poetry law music morality history ref name yeakel john '' https coreacuk download pdf pdf accountant historians incas '' accounting historians journal volume issue fall article ref ref name adames hector chavez due nayeli ''cultural foundations interventions latino mental health history theory within group differences'' pp routledge ref young inca nobles educated disciplines state college yacha huasi cuzco also learned art quipu ref name


st century many suggest gem anscombe hannah arendt simone de beauvoir susanne langer entered canon ref name duran jane duran jane eight women philosophers theory politics feminism university illinois press ref ref name readhipporeadscom ref section end women philosophy intro early colleges universities uk us began admitting women producing female academics nevertheless us department education reports indicate women ended philosophy philosophy one least gender proportionate fields humanities women making somewhere


philosophy faculty according studies ref name salary promotion salary promotion tenure status minority women faculty us colleges universities national center education statistics statistical analysis report march us department education office education research improvement report nces national study postsecondary faculty nsopf see also characteristics attitudes instructional faculty staff humanities national center education statistics ed tabs july us department education office education research improvement report nces national study postsecondary faculty nsopf ref philosophical progress many


philosophical debates began ancient times still debated today british philosopher colin mcginn claims philosophical progress occurred interval australian philosopher david chalmers contrast sees progress philosophy similar science meanwhile talbot brewer professor philosophy university virginia argues progress wrong standard judge philosophical activity branches philosophy span id branches span philosophical questions grouped various branches groupings allow philosophers focus set similar topics interact thinkers interested


questions divisions neither exhaustive mutually exclusive philosopher might specialize kantian epistemology platonic aesthetics modern political philosophy furthermore philosophical inquiries sometimes overlap inquiries science religion mathematics aesthetics aesthetics critical reflection art culture nature addresses nature art beauty taste enjoyment emotional values perception creation appreciation beauty precisely defined study sensory sensori emotional values sometimes called judgments sentiment taste major divisions


art theory literary theory film theory music theory example art theory discern set principles underlying work particular artist artistic movement cubist aesthetic ethics beijing imperial college intellectual center confucian ethics classics yuan ming qing dynasties ethics also known moral philosophy studies constitutes good bad conduct right wrong values good evil primary investigations include live good life identifying standards morality also includes investigating whether


''is'' best way live universal moral standard come learn main branches ethics normative ethics meta ethics applied ethics ref name iep ethics ref three main views ethics constitute moral actions ref name iep ethics consequentialism judges actions based consequences ref name auto ref one view utilitarianism judges actions based net happiness pleasure lack suffering pain produce deontology judges actions based whether accordance one 's


moral duty ref name auto standard form defended immanuel kant deontology concerned whether choice respects moral agency people regardless consequences ref name auto virtue ethics judges actions based moral character agent performs whether conform ideally virtuous agent would ref name auto epistemology dignaga founded school buddhist epistemology logic epistemology branch philosophy studies knowledge ref name britannica ref epistemologists examine putative sources knowledge including perceptual experience reason memory testimony also investigate questions


nature truth belief justification rationality ref name sep epistemology ref philosophical skepticism raises doubts claims knowledge topic interest throughout history philosophy arose early pre socratic philosophy became formalized pyrrho founder earliest western school philosophical skepticism features prominently works modern philosophers ren descartes david hume remained central topic contemporary epistemological debates ref name sep epistemology one notable epistemological debates empiricism rationalism ref name auto ref empiricism places emphasis observational evidence


via sensory experience source knowledge ref name auto empiricism associated posteriori knowledge obtained experience scientific knowledge ref name auto rationalism places emphasis reason source knowledge ref name auto rationalism associated priori knowledge independent experience logic mathematics one central debate contemporary epistemology conditions required belief constitute knowledge might include truth justification debate largely result attempts solve gettier problem ref name sep epistemology another common subject contemporary debates


general features reality existence time objects properties wholes parts events processes causation relationship mind body metaphysics includes cosmology study world entirety ontology study major point debate realism holds entities exist independently mental perception idealism holds reality mentally constructed otherwise immaterial metaphysics deals topic identity essence set attributes make object fundamentally


mind relationship body typified disputes materialism dualism recent years branch become related cognitive science philosophy science philosophy science explores foundations methods history implications purpose science many subdivisions correspond specific branches science example philosophy biology deals specifically metaphysical epistemological ethical issues biomedical life sciences political philosophy thomas hobbes best known ''leviathan'' expounded influential formulation social contract theory political philosophy


study government relationship individuals families clans communities including state ref name auto ref includes questions justice law property rights obligations citizen ref name auto political philosophy ethics aesthetics traditionally linked subjects general heading value theory involve normative evaluative aspect philosophy religion philosophy religion deals questions involve religion religious ideas philosophically neutral perspective opposed theology begins religious convictions traditionally religious questions seen separate field philosophy proper


idea separate field arose th century ref group lower roman wainwright william j introduction pp '' https booksgoogleca booksid gbcucf tldgc oxford handbook philosophy religion '' edited w j wainwright new york oxford university press expression philosophy religion come general use nineteenth century employed refer articulation criticism humanity 's religious consciousness cultural expressions thought language feeling practice ref issues include existence god relationship reason faith questions religious epistemology relationship religion


science interpret religious experiences questions possibility afterlife problem religious language existence souls responses religious pluralism diversity metaphilosophy metaphilosophy explores aims boundaries methods philosophy debated whether metaphilosophy subject comes prior philosophy whether inherently part philosophy applied professional philosophy martin luther king jr study philosophy become professional philosophers typically working professors teach research write academic institutions however students


academic philosophy later contribute law journalism religion sciences politics business various arts ref name whystudyphilosophycom ref example public figures degrees philosophy include comedians steve martin ricky gervais filmmaker terrence malick pope john paul ii wikipedia co founder larry sanger technology entrepreneur peter thiel us supreme court justice stephen bryer us vice presidential candidate carly fiorina curtis white argued philosophical tools essential humanities sciences social sciences recent efforts avail general public work relevance philosophers include million dollar berggruen prize first awarded charles taylor


philosophers argue professionalization negatively affected discipline see also list important publications philosophy list years philosophy list philosophy journals list philosophy awards list unsolved problems philosophy lists philosophers social theory references notes citations quote philosophy rationally critical thinking less systematic kind general nature world metaphysics theory existence justification belief epistemology theory knowledge conduct life ethics theory value


three elements list non philosophical counterpart distinguished explicitly rational critical way proceeding systematic nature everyone general conception nature world live place metaphysics replaces unargued assumptions embodied conception rational organized body beliefs world whole everyone occasion doubt question beliefs others less success without theory


epistemology seeks argument make explicit rules correct belief formation everyone governs conduct directing desired valued ends ethics moral philosophy inclusive sense seeks articulate rationally systematic form rules principles involved ref ref name online etymology dictionary ref ref name process ''process reality'' p ref ref name webster 's new world dictionary definition philosophy orig love search wisdom knowledge theory logical analysis principles underlying conduct thought knowledge nature universe ref


bibliography year publisher macmillan free press year publisher macmillan year publisher oxford university press incorporated isbn date publisher cambridge university press isbn date publisher oxford university press isbn date publisher john wiley sons isbn date publisher cambridge university press isbn year publisher cambridge university press isbn date publisher oxford university press date publisher john wiley sons isbn year publisher paulist press isbn last leaman first oliver author link oliver leaman first parviz last morewedge chapter islamic philosophy modern editor first edward editor last craig publisher psychology press year isbn url https archiveorg details conciseroutledge edwa reading general introduction blumenau ralph ''philosophy living'' craig edward ''philosophy short introduction'' harrison barbet anthony ''mastering philosophy'' russell bertrand '' https webarchiveorg web http philosophyhkuhk think phil russell problems philosophy '' sinclair alistair j ''what philosophy introduction'' sober elliott ''core questions philosophy text readings'' upper saddle


river prentice hall solomon robert c ''big questions short introduction philosophy'' warburton nigel ''philosophy basics'' nagel thomas ''what mean short introduction philosophy'' ''classics philosophy vols '' louis p pojman cottingham john western philosophy anthology nd ed malden blackwell pub print blackwell philosophy anthologies tarnas richard ''the passion western mind understanding ideas shaped world view'' topical introductions african imbo samuel oluoch ''an introduction african philosophy'' eastern ''a source book indian philosophy'' sarvepalli radhakrishnan


charles moore hamilton sue ''indian philosophy short introduction'' kupperman joel j ''classic asian philosophy guide essential texts'' lee joe powell jim ''eastern philosophy beginners'' smart ninian ''world philosophies'' copleston frederick ''philosophy russia herzen lenin berdyaev'' islamic ''medieval islamic philosophical writings'' edited muhammad ali khalidi date june publisher taylor francis isbn translator first liadain translator last sherrard translator first philip translator last sherrard translator link philip sherrard orig year date december publisher routledge isbn historical introductions general higgins kathleen solomon robert c ''a short history philosophy'' durant ''story philosophy lives opinions world 's greatest philosophers'' pocket ancient


knight kelvin ''aristotelian philosophy ethics politics aristotle macintyre'' medieval ''the phenomenology reader'' dermot moran timothy mooney kim j ernest sosa ed ''metaphysics anthology'' blackwell philosophy anthologies oxford blackwell publishers ltd year publisher indiana university press isbn modern contemporary ''the english philosophers bacon mill'' edwin arthur ''european philosophers descartes nietzsche'' monroe beardsley ''existentialism basic writings second edition '' charles guignon derk pereboom curley edwin ''a spinoza reader'' princeton bullock alan rb woodings john cumming ''eds'' ''the fontana dictionary modern thinkers'' series ''fontana original '' hammersmith eng fontana


press xxv p scruton roger ''a short history modern philosophy'' ''contemporary analytic philosophy core readings'' james baillie appiah kwame anthony ''thinking nbsp nbsp introduction contemporary philosophy'' critchley simon ''continental philosophy short introduction'' reference works ''the cambridge dictionary philosophy'' robert audi ''the routledge encyclopedia philosophy'' vols edited edward craig luciano floridi available online subscription ''the concise routledge encyclopedia philosophy'' edited edward craig abridgement year publisher macmillan free press ninth supplemental volume appeared updated


classic encyclopedia ''international directory philosophy philosophers'' charlottesville philosophy documentation center ''directory american philosophers'' charlottesville philosophy documentation center ''routledge history philosophy'' vols edited john marenbon ''history philosophy'' vols frederick copleston ''a history western philosophy'' vols wt jones ''history italian philosophy'' vols eugenio garin translated italian edited giorgio pinton introduction leon pompa ''encyclopaedia indian philosophies'' vols edited karl h potter et al first volumes print ''indian philosophy'' vols sarvepalli radhakrishnan ''a history indian


philosophy'' vols surendranath dasgupta ''history chinese philosophy'' vols fung yu lan derk bodde ''instructions practical living neo confucian writings wang yang ming'' chan wing tsit ''encyclopedia chinese philosophy'' edited antonio cua ''encyclopedia eastern philosophy religion'' ingrid fischer schreiber franz karl ehrhard kurt friedrichs ''companion encyclopedia asian philosophy'' brian carr indira mahalingam ''a concise dictionary indian philosophy sanskrit terms defined english'' john grimes ''history islamic philosophy'' edited seyyed hossein nasr oliver leaman ''history jewish philosophy'' edited daniel h frank oliver leaman


''a history russian philosophy tenth twentieth centuries'' valerii aleksandrovich kuvakin ayer aj et al ed ''a dictionary philosophical quotations'' blackwell reference oxford oxford basil blackwell ltd blackburn ed ''the oxford dictionary philosophy'' oxford oxford university press mautner ed ''the penguin dictionary philosophy'' london penguin books runes ed http wwwditextcom runes ''the dictionary philosophy'' new york philosophical library inc angeles pa ed ''the harper collins dictionary philosophy'' new york harper perennial date april publisher john wiley sons isbn hoffman eric ed ''guidebook publishing


''the parnassus'' raphael famous poets recite alongside nine muses atop mount parnassus '''poetry''' derived greek ''poiesis'' making form literature uses aesthetic often rhythmic qualities language phonaesthetics sound symbolism metre evoke meanings addition place prosaic ostensible meaning '''poem''' literary composition written utilising principle poetry long varied history evolving differentially across globe dates back least prehistoric times hunting poetry africa panegyric elegiac

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poem open multiple interpretations similarly figures speech metaphor simile metonymy establish resonance otherwise disparate images layering meanings forming connections previously perceived kindred forms resonance may exist individual verses patterns rhyme rhythm poetry types unique particular cultures genres respond characteristics language poet writes readers accustomed identifying poetry dante goethe mickiewicz rumi may think written lines based rhyme regular meter however traditions biblical


poetry use means create rhythm euphony much modern poetry reflects critique poetic tradition testing principle euphony altogether forgoing rhyme set rhythm increasingly globalized world poets often adapt forms styles techniques diverse cultures languages poets contributed evolution linguistic expressive utilitarian qualities languages western cultural tradition extending least homer rilke associates production poetry inspiration often muse either classical contemporary history early works


scholars believe art poetry may predate literacy developed folk epics oral genres others however suggest poetry necessarily predate writing ref name goody jack ref oldest surviving epic poem ''epic gilgamesh'' dates rd millenniumbce sumer mesopotamia present day iraq written cuneiform script clay tablets later papyrus istanbul tablet dating bce describes annual rite king symbolically married mated goddess inanna ensure fertility prosperity labelled world 's


oldest love poem ref name oldest poem ref example egyptian epic poetry ''the story sinuhe'' c bce ancient epics includes greek ''iliad'' ''odyssey'' persian avestan books ''yasna'' roman national epic virgil 's ''aeneid'' written bce indian epics ''ramayana'' ''mahabharata'' epic poetry appears composed poetic form aid memorization oral transmission ancient societies ref name goody jack forms poetry including ancient collections religious hymns indian sanskrit language ''rigveda'' avestan ''gathas''


''hurrian songs'' hebrew ''psalms'' possibly developed directly folk songs earliest entries oldest extant collection chinese poetry ''classic poetry'' ''shijing'' initially lyrics ref name ebrey ref shijing collection poems folk songs heavily valued philosopher confucius considered one official confucian classics remarks subject become invaluable source ancient music theory efforts ancient thinkers determine makes poetry distinctive form distinguishes good poetry bad resulted poetics study


aesthetics poetry ancient societies china 's ''shijing'' developed canons poetic works ritual well aesthetic importance recently thinkers struggled find definition could encompass formal differences great chaucer 's ''canterbury tales'' matsuo bash 's ''oku hosomichi'' well differences content spanning tanakh religious poetry love poetry rap gallery mode packed heights file oldest love poem sumerian terracotta tablet nippur iraq ur iii period bce ancient orient museum istanbuljpg oldest known love poem sumerian terracotta tablet


nippur iraq ur iii period bce ancient orient museum istanbul file confucius scholarjpg philosopher confucius influential developed approach poetry ancient music theory file manuscript shanghai museum jpg early chinese poetics ''k ngz sh l n'' discussing ''shijing'' ''classic poetry'' gallery western traditions aristotle classical thinkers west employed classification way define assess quality poetry notably existing fragments aristotle 's ''poetics'' describe three genres poetry epic comic tragic develop rules distinguish highest quality poetry genre based


perceived underlying purposes genre later aestheticians identified three major genres epic poetry lyric poetry dramatic poetry treating comedy tragedy subgenres dramatic poetry john keats aristotle 's work influential throughout middle east islamic golden age well europe renaissance later poets aestheticians often distinguished poetry defined opposition prose generally understood writing proclivity logical explication linear narrative structure imply poetry illogical lacks narration rather poetry


attempt render beautiful sublime without burden engaging logical narrative thought process english romantic poet john keats termed escape logic negative capability romantic approach views form key element successful poetry form abstract distinct underlying notional logic approach remained influential th century th th centuries also substantially interaction among various poetic traditions part due spread european colonialism attendant rise global trade addition boom


translation romantic period numerous ancient works rediscovered th century st century disputes archibald macleish th century literary theorists rely less ostensible opposition prose poetry instead focusing poet simply one creates using language poetry poet creates underlying concept poet creator uncommon modernist poets essentially distinguish creation poem words creative acts media yet modernists challenge attempt define poetry misguided rejection traditional


forms structures poetry began first half th century coincided questioning purpose meaning traditional definitions poetry distinctions poetry prose particularly given examples poetic prose prosaic poetry numerous modernist poets written non traditional forms traditionally would considered prose although writing generally infused poetic diction often rhythm tone established non metrical means substantial formalist reaction within modernist schools breakdown structure reaction focused


much development new formal structures syntheses revival older forms structures postmodernism goes beyond modernism 's emphasis creative role poet emphasize role reader text hermeneutics highlight complex cultural web within poem read today throughout world poetry often incorporates poetic form diction cultures past confounding attempts definition classification made sense within tradition western canon early st century poetic tradition appears


continue strongly orient earlier precursor poetic traditions initiated whitman emerson wordsworth literary critic geoffrey hartman used phrase anxiety demand describe contemporary response older poetic traditions fearful fact longer form building trope introduced emerson emerson maintained debate concerning poetic structure either form fact could predominate one need simply ask fact form challenged various levels literary scholars bloom


stated generation poets stand together mature ready write major american verse twenty first century may yet seen stevens called 'a great shadow 's last embellishment' shadow emerson 's elements prosody prosody study meter rhythm intonation poem rhythm meter different although closely related meter definitive pattern established verse iambic pentameter rhythm actual sound results line poetry prosody also may used


languages pitch accent vedic sanskrit ancient greek tonal languages include chinese vietnamese subsaharan languages metrical rhythm generally involves precise arrangements stresses syllables repeated patterns called feet within line modern english verse pattern stresses primarily differentiate feet rhythm based meter modern english often founded pattern stressed unstressed syllables alone elided classical languages hand metrical units similar vowel length rather stresses define meter old english poetry used