Planck_constant

qas: question: What is energy abbreviated to in science?
answers: text: E

question: What is frequency also known as in science?
answers: text: f

question: What term describes a small amount of element?
answers: text: quantum

question: What did the light quantum, in some ways, behave as?
answers: text: an electrically neutral particle

question: What was later termed the photon?
answers: text: The light quantum

question: When did Max Planck first recognize the value of the Planck constant?
answers: text: 1900

question: Which scientist associated the Planck constant with a quantum five years after Planck's recognition?
answers: text: Einstein

question: Instead of an electromagnetic wave, what did the light quantum behave as in some regards?
answers: text: an electrically neutral particle

question: What is the simple name given to the light quantum today?
answers: text: the photon

question: In what year was the value G associated by Einstein with quantum theories of energy?

question: Who discovered an association between the value G and quantum energy?

question: What type of charge did a particle have that behaved similarly to dark quantum energy?

question: What term describes a large amount of element?

question: What is the simple name given to the dark quantum today?
context: First recognized in 1900 by Max Planck, it was originally the proportionality constant between the minimal increment of energy, E, of a hypothetical electrically charged oscillator in a cavity that contained black body radiation, and the frequency, f, of its associated electromagnetic wave. In 1905 the value E, the minimal energy increment of a hypothetical oscillator, was theoretically associated by Einstein with a "quantum" or minimal element of the energy of the electromagnetic wave itself. The light quantum behaved in some respects as an electrically neutral particle, as opposed to an electromagnetic wave. It was eventually called the photon.

qas: question: Classical statistical mechanics requires the existence of what?
answers: text: h

question: What was realized after Planck's discovery?
answers: text: that physical action cannot take on an arbitrary value

question: What is the Planck constant formerly known as?
answers: text: quantum of action

question: Regarding atoms, what does the Planck constant imply?
answers: text: that only certain energy levels are allowed

question: Regarding atoms, what are values in between certain energy levels considered by the Planck constant?
answers: text: forbidden

question: Following Planck's discovery, what was realized about values of physical action?
answers: text: physical action cannot take on an arbitrary value

question: The Planck constant initially was given what name?
answers: text: the "quantum of action"

question: How is the proportional nature of the Planck constant explained?
answers: text: Classical physics cannot explain this fact

question: For certain cases of light or atoms, what does the quantum of action yield?
answers: text: only certain energy levels are allowed, and values in between are forbidden.

question: What does modern statistics mechanics not define the value of?

question: What is not required to exist in modern statistics mechanics?

question: What does the Planck Constant negate?

question: What is the Planck constant incorrectly known as?

question: Which science is the proportional nature of the Planck constant fact?
context: Classical statistical mechanics requires the existence of h (but does not define its value). Eventually, following upon Planck's discovery, it was recognized that physical action cannot take on an arbitrary value. Instead, it must be some multiple of a very small quantity, the "quantum of action", now called the Planck constant. Classical physics cannot explain this fact. In many cases, such as for monochromatic light or for atoms, this quantum of action also implies that only certain energy levels are allowed, and values in between are forbidden.

qas: question: What does the smallness of the Planck constant show?
answers: text: the fact that everyday objects and systems are made of a large number of particles

question: At about what wavelength of light are human eyes most sensitive?
answers: text: 555 nanometres

question: What frequency does green light with a wavelength of 555 nanmetres have?
answers: text: 7014540000000000000♠540 THz

question: How is the energy from one mole of photos computed?
answers: text: by multiplying the photon energy by the Avogadro constant

question: How much energy does a green light of wavelength 555 nm contain?
answers: text: 7005216000000000000♠216 kJ/mol

question: What is the wavelength of light to which human eyes are most sensitive?
answers: text: 555 nanometres

question: What is the frequency of the light to which the human eye is most sensitive?
answers: text: 7014540000000000000♠540 THz

question: What is the energy of a photon?
answers: text: 6981358000000000000♠3.58×10−19 J

question: How much energy is contained in the light to which human eyes are most sensitive?
answers: text: 7005216000000000000♠216 kJ/mol

question: What are common things like furniture and stationary objects never made of?

question: Which light wavelength is the human eye no longer able to see?

question: What color of light is the human eye blind to?

question: What does the smallness of the Planck constant ignore?
context: Equivalently, the smallness of the Planck constant reflects the fact that everyday objects and systems are made of a large number of particles. For example, green light with a wavelength of 555 nanometres (the approximate wavelength to which human eyes are most sensitive) has a frequency of 7014540000000000000♠540 THz (7014540000000000000♠540×1012 Hz). Each photon has an energy E = hf = 6981358000000000000♠3.58×10−19 J. That is a very small amount of energy in terms of everyday experience, but everyday experience is not concerned with individual photons any more than with individual atoms or molecules. An amount of light compatible with everyday experience is the energy of one mole of photons; its energy can be computed by multiplying the photon energy by the Avogadro constant, NA ≈ 7023602200000000000♠6.022×1023 mol−1. The result is that green light of wavelength 555 nm has an energy of 7005216000000000000♠216 kJ/mol, a typical energy of everyday life.

qas: question: What was Planck studying in the last part of the nineteenth century?
answers: text: the problem of black-body radiation

question: Who posed the problem of black-body radiation?
answers: text: Kirchhoff

question: Cooler objects glow less than objects that are what?
answers: text: hotter

question: What does a black object do to any of the light that hits it?
answers: text: it absorbs all the light

question: What is maximized as a result of a black object absorbing all the light that hits it?
answers: text: thermal light emission

question: Planck studied what problem posed originally by Kirchhoff?
answers: text: black-body radiation

question: If an object is black, what is known about its thermal light emission?
answers: text: its thermal light emission is maximized.

question: What is known about the light absorption of a hot object in equilibrium with light?
answers: text: absorbs just as much light as it emits

question: Electromagnetic fields obey what laws?
answers: text: laws of motion

question: What type of radiation was Planck studying in the late 18th century?

question: How many years prior to Planck's study had the scientific community first avoided black body radiation?

question: What scientist never studied black body radiation?

question: What is required for the electromagnetic field to come to thermal differences?

question: What does a hot object in equilibrium reflect as much as it emits?
context: In the last years of the nineteenth century, Planck was investigating the problem of black-body radiation first posed by Kirchhoff some forty years earlier. It is well known that hot objects glow, and that hotter objects glow brighter than cooler ones. The electromagnetic field obeys laws of motion similarly to a mass on a spring, and can come to thermal equilibrium with hot atoms. The hot object in equilibrium with light absorbs just as much light as it emits. If the object is black, meaning it absorbs all the light that hits it, then its thermal light emission is maximized.

qas: question: What assumption that black-body radiation is what leads to an accurate prediction?
answers: text: thermal

question: What does the Stefan-Boltzmann law state?
answers: text: the total amount of emitted energy goes up with the temperature according to a definite rule

question: What about a hot object changes with the temperature?
answers: text: the colour of the light

question: What color is hotter than "red hot"?
answers: text: white hot

question: What did Wilhelm Wien discover?
answers: text: the mathematical relationship between the peaks of the curves at different temperatures

question: What rule predicts that emitted energy increases with temperature?
answers: text: the Stefan–Boltzmann law

question: What characteristic of the light emitted by a hot object changes with temperature?
answers: text: the colour of the light given off

question: Who discovered the mathematical relationship between peaks and curves of light at different temperatures?
answers: text: Wilhelm Wien

question: The rule that adjust the curve at different temperatures is known as what?
answers: text: Wien's displacement law

question: Wien's spectrum model could not predict accurate at what end of the spectrum?
answers: text: at low frequencies (long wavelength)

question: What do scientists assume black body radiation is never made from?

question: What law describes the changes in light emitted by a frozen object?

question: What about a frozen object changes with the temperature?

question: What rule predicts that emitted energy decreases with temperature?

question: What law adjusts the curve at the same temperatures?
context: The assumption that black-body radiation is thermal leads to an accurate prediction: the total amount of emitted energy goes up with the temperature according to a definite rule, the Stefan–Boltzmann law (1879–84). But it was also known that the colour of the light given off by a hot object changes with the temperature, so that "white hot" is hotter than "red hot". Nevertheless, Wilhelm Wien discovered the mathematical relationship between the peaks of the curves at different temperatures, by using the principle of adiabatic invariance. At each different temperature, the curve is moved over by Wien's displacement law (1893). Wien also proposed an approximation for the spectrum of the object, which was correct at high frequencies (short wavelength) but not at low frequencies (long wavelength). It still was not clear why the spectrum of a hot object had the form that it has (see diagram).

qas: question: Before Planck, it was assumed that the energy of a body could take on what value?
answers: text: any

question: The Rayleigh-Jeans law makes close predictions for what amount of values?
answers: text: a narrow range

question: What does Planck's law correctly predict?
answers: text: blackbody emissions

question: In making Planck's law, what was in both the numerator and denominator of the formula that was used?
answers: text: h

question: Planck's work disproved what assumption?
answers: text: that the energy of a body could take on any value whatsoever

question: What rule predicted narrow range of energy values at lower temperatures?
answers: text: The Rayleigh–Jeans

question: Planck's law involved what necessary mathematical step to correctly predict blackbody emission?
answers: text: multiply the classical expression by a complex factor that involves h in both the numerator and the denominator

question: Changing values of n, the Boltzmann constant, or other variables resulted in learning what about Planck's law?
answers: text: Making an equation out of Planck's law that would reproduce the Rayleigh–Jeans law could not be done

question: The disparity between Planck's law and the Rayleigh-Jeans law led to what conclusion?
answers: text: the picture given by classical physics is not duplicated by a range of results in the quantum picture

question: What was assumed that the energy of a body could never take on before Planck?

question: What does the Rayleigh-Jeans law avoid predictions for in terms of values?

question: What does Planck's law incorrectly predict?

question: What in making Planck's law was in neither the numerator and denominator of the formula that was used?

question: What assumption was confirmed based on Planck's work?
context: Prior to Planck's work, it had been assumed that the energy of a body could take on any value whatsoever – that it was a continuous variable. The Rayleigh–Jeans law makes close predictions for a narrow range of values at one limit of temperatures, but the results diverge more and more strongly as temperatures increase. To make Planck's law, which correctly predicts blackbody emissions, it was necessary to multiply the classical expression by a complex factor that involves h in both the numerator and the denominator. The influence of h in this complex factor would not disappear if it were set to zero or to any other value. Making an equation out of Planck's law that would reproduce the Rayleigh–Jeans law could not be done by changing the values of h, of the Boltzmann constant, or of any other constant or variable in the equation. In this case the picture given by classical physics is not duplicated by a range of results in the quantum picture.

qas: question: Einstein and what other two individuals revisited the black-body problem in 1905?
answers: text: Rayleigh and Jeans

question: Who came up with the term, "ultraviolet catastrophe"?
answers: text: Paul Ehrenfest

question: When did Paul Ehrenfest come up with the name "ultraviolet catastrophe"?
answers: text: 1911

question: When was the first Solvay Conference held?
answers: text: 1911

question: Who received the Nobel Prize in Physics in 1918?
answers: text: Max Planck

question: What did Rayleigh & Jeans and Einstein prove independently in 1905?
answers: text: classical electromagnetism could never account for the observed spectrum

question: What name did Paul Ehrenfest give to the proofs from Einstein and Rayleigh & Jeans?
answers: text: the "ultraviolet catastrophe"

question: When was the first Solvay Conference held?
answers: text: 1911

question: What was the topic of the first Solvay Conference?
answers: text: "the theory of radiation and quanta"

question: In what year did Planck receive the Nobel Prize in Physics for his discovery of energy quanta?
answers: text: 1918

question: What other two individuals aside from Einstein revisited the black-body problem in 1945?

question: Who never used the term, "ultraviolet catastrophe"?

question:  When was the last Solvay Conference held?

question: Who refused the Nobel Prize in Physics in 1918?

question: Who received the Nobel Prize in Physics based on the destruction of energy quanta?
context: The black-body problem was revisited in 1905, when Rayleigh and Jeans (on the one hand) and Einstein (on the other hand) independently proved that classical electromagnetism could never account for the observed spectrum. These proofs are commonly known as the "ultraviolet catastrophe", a name coined by Paul Ehrenfest in 1911. They contributed greatly (along with Einstein's work on the photoelectric effect) to convincing physicists that Planck's postulate of quantized energy levels was more than a mere mathematical formalism. The very first Solvay Conference in 1911 was devoted to "the theory of radiation and quanta". Max Planck received the 1918 Nobel Prize in Physics "in recognition of the services he rendered to the advancement of Physics by his discovery of energy quanta".

qas: question: Who first observed the photoelectric effect?
answers: text: Alexandre Edmond Becquerel

question: When was the photoelectric effect first observed?
answers: text: 1839

question: Who published the first thorough investigation of the photoelectric effect?
answers: text: Heinrich Hertz

question: Who received the Nobel Prize in 1921 for his work on the photoelectric effect?
answers: text: Einstein

question: What did Einstein with the 1921 Nobel Prize for?
answers: text: his work on the photo-electric effect

question: What is the photoelectric effect?
answers: text: the emission of electrons (called "photoelectrons") from a surface when light is shone on it

question: Who first observed the photoelectric effect?
answers: text: Alexandre Edmond Becquerel

question: Einstein's paper on the photoelectric effect earned him the Nobel Prize in what year?
answers: text: 1921

question: Einstein's photoelectric effect work was rewards as opposed to his work on what other topic?
answers: text: relativity

question: Who last observed the photoelectric effect?

question: When was the photoelectric effect last observed?

question: Who published the first thorough investigation of the photosynthesis effect?

question: What did Einstein win the 1924 Nobel Prize for?

question: What is the photoneutral effect?
context: The photoelectric effect is the emission of electrons (called "photoelectrons") from a surface when light is shone on it. It was first observed by Alexandre Edmond Becquerel in 1839, although credit is usually reserved for Heinrich Hertz, who published the first thorough investigation in 1887. Another particularly thorough investigation was published by Philipp Lenard in 1902. Einstein's 1905 paper discussing the effect in terms of light quanta would earn him the Nobel Prize in 1921, when his predictions had been confirmed by the experimental work of Robert Andrews Millikan. The Nobel committee awarded the prize for his work on the photo-electric effect, rather than relativity, both because of a bias against purely theoretical physics not grounded in discovery or experiment, and dissent amongst its members as to the actual proof that relativity was real.

qas: question: Before Einstein, electromagnetic radiation was considered to behave as what?
answers: text: a wave

question: What terms describe different types of radiation?
answers: text: "frequency" and "wavelength"

question: What is the energy transferred by a wave in a given time called?
answers: text: intensity

question: What other types of wave besides light has its own intensity?
answers: text: sound

question: Prior to Einstein's work, light behavior was modeled as what?
answers: text: a wave

question: What is the name for the amount of energy transfered by a wave in a given time?
answers: text: intensity

question: What portion of the photoelectric effect was in disagreement with the believed description of light behavior?
answers: text: the energy account

question: What does it mean for a light source to be more intense than another?
answers: text: gives out more energy per unit time and per unit space

question: What terms describe the same types of radiation?

question: What is the energy lost by a wave in a long time called?

question: What other types of wave besides light doesn't have its own intensity?

question: What is the name for the amount of energy disappearing by a wave in a given time?

question: What does it mean for a light source to be equally intense?
context: Prior to Einstein's paper, electromagnetic radiation such as visible light was considered to behave as a wave: hence the use of the terms "frequency" and "wavelength" to characterise different types of radiation. The energy transferred by a wave in a given time is called its intensity. The light from a theatre spotlight is more intense than the light from a domestic lightbulb; that is to say that the spotlight gives out more energy per unit time and per unit space(and hence consumes more electricity) than the ordinary bulb, even though the colour of the light might be very similar. Other waves, such as sound or the waves crashing against a seafront, also have their own intensity. However, the energy account of the photoelectric effect didn't seem to agree with the wave description of light.

qas: question: What is emitted as a result of the photoelectric effect?
answers: text: photoelectrons

question: What does the kinetic energy of a photoelectron depend on?
answers: text: the frequency

question: What happens if the photoelectron's frequency is too low?
answers: text: no photoelectrons are emitted at all

question: What is the term used when photoelectrons act virtually at the same time?
answers: text: multiphoton effect

question: What type of energy due photoelectrons emitted due to the photoelectric effect have?
answers: text: kinetic

question: What factor of the initial light source does the energy of the photoelectrons depend on?
answers: text: frequency

question: When the photon energy is less than the work function of the material the light is shone upon, how many photoelectrons are emitted?
answers: text: no photoelectrons are emitted at all

question: If the photoelectric effect is occuring, increasing the intensity of the light source causes what?
answers: text: more photoelectrons to be emitted with the same kinetic energy

question: What is infused as a result of the photoneutral effect?

question: What does the kinetic energy of a photoelectron lose?

question: What happens if the photoelectron's frequency stays the same?

question: What type of energy due photoelectrons emitted due to the photoneutral effect have?
context: The "photoelectrons" emitted as a result of the photoelectric effect have a certain kinetic energy, which can be measured. This kinetic energy (for each photoelectron) is independent of the intensity of the light, but depends linearly on the frequency; and if the frequency is too low (corresponding to a photon energy that is less than the work function of the material), no photoelectrons are emitted at all, unless a plurality of photons, whose energetic sum is greater than the energy of the photoelectrons, acts virtually simultaneously (multiphoton effect)  Assuming the frequency is high enough to cause the photoelectric effect, a rise in intensity of the light source causes more photoelectrons to be emitted with the same kinetic energy, rather than the same number of photoelectrons to be emitted with higher kinetic energy.

qas: question: Who introduced the first quantized model of the atom?
answers: text: Niels Bohr

question: When was the first quantized model of the atom introduced?
answers: text: 1913

question: Why was the first quantized model of the atom introduced?
answers: text: to overcome a major shortcoming of Rutherford's classical model

question: In classical electrodynamics, a charge moving in a circle should do what?
answers: text: radiate electromagnetic radiation

question: Who modeled the atom in 1913, challenging Rutherford's model?
answers: text: Niels Bohr

question: What was predicted to happen to a nucleus-orbiting electron under Rutherford's model?
answers: text: the radiation would cause it to lose energy and spiral down into the nucleus

question: What statement did Bohr make about the electron of an atom, citing Planck's work?
answers: text: an electron in a Bohr atom could only have certain defined energies

question: Who introduced the last quantized model of the atom?

question: When was the last quantized model of the molecule introduced?

question: Why was the first quantized model of the atom destroyed?

question: Who modeled the molecule in 1918, challenging Rutherford's model?

question: What statement did Bohr make about the nucleus of an atom?
context: Niels Bohr introduced the first quantized model of the atom in 1913, in an attempt to overcome a major shortcoming of Rutherford's classical model. In classical electrodynamics, a charge moving in a circle should radiate electromagnetic radiation. If that charge were to be an electron orbiting a nucleus, the radiation would cause it to lose energy and spiral down into the nucleus. Bohr solved this paradox with explicit reference to Planck's work: an electron in a Bohr atom could only have certain defined energies En

qas: question: Who introduced the reduced Planck constant?
answers: text: Bohr

question: What is the reduced Planck constant also known as?
answers: text: the quantity

question: Who helped to give the correct quantization rules for electrons in 1925?
answers: text: Heisenberg

question: Who helped to give the correct quantization rules for electrons in 1926?
answers: text: Schrödinger

question: According to Heisenberg and Schrödinger, the reduced Planck constant remains what?
answers: text: the fundamental quantum of angular momentum

question: Bohr introduced what value as the quantum of angular momentum?
answers: text: the reduced Planck constant

question: What incorrect belief did Bohr hold about the reduced Planck constant?
answers: text: Bohr thought that this was the angular momentum of each electron in an atom

question: What scientist used matrix mechanics to bring electron behavior in line with the Bohr model?
answers: text: Heisenberg

question: When was the Schrödinger wave equation proposed?
answers: text: 1926

question: Who reduced the increased Planck constant?

question: What is the extended Planck constant also known as?

question:  Who helped to give the correct quantization rules for electrons in 1945?

question: Who helped to give the incorrect quantization rules for electrons in 1946?

question: What scientist used matrix mechanics to bring wave behavior against the Bohr model?
context: Bohr also introduced the quantity , now known as the reduced Planck constant, as the quantum of angular momentum. At first, Bohr thought that this was the angular momentum of each electron in an atom: this proved incorrect and, despite developments by Sommerfeld and others, an accurate description of the electron angular momentum proved beyond the Bohr model. The correct quantization rules for electrons – in which the energy reduces to the Bohr model equation in the case of the hydrogen atom – were given by Heisenberg's matrix mechanics in 1925 and the Schrödinger wave equation in 1926: the reduced Planck constant remains the fundamental quantum of angular momentum. In modern terms, if J is the total angular momentum of a system with rotational invariance, and Jz the angular momentum measured along any given direction, these quantities can only take on the values

qas: question:  What measurable value obeys a similar rule of angular momentum?
answers: text: time vs. energy

question: What forces measurement attempts to choose between trade-offs, in quanta?
answers: text: either-or nature of uncertainty

question: What form do measurement attempt trade-offs for quanta take the form of?
answers: text: either-or (as in Fourier analysis)

question: How is uncertainly measured in this experience?
answers: text: the standard deviation of the measured value from its expected value

question: What type of analysis fits the either-or nature of the uncertainty?
answers: text: Fourier analysis

question: What example is given as another paired relationship of uncertainly related to standard deviation?
answers: text: time vs. energy

question: What measurable value avoids a similar rule of angular momentum?

question: What forces measurement never chooses between trade-offs, in quanta?

question: What form do measurement attempt trade-offs for quanta avoid?

question: What type of analysis fits the either-and nature of certainty?

question: What example is given as another paired relationship of certainty related to deviation?
context: where the uncertainty is given as the standard deviation of the measured value from its expected value. There are a number of other such pairs of physically measurable values which obey a similar rule. One example is time vs. energy. The either-or nature of uncertainty forces measurement attempts to choose between trade offs, and given that they are quanta, the trade offs often take the form of either-or (as in Fourier analysis), rather than the compromises and gray areas of time series analysis.

qas: question: What is the unit of magentic properties of the electron?
answers: text: Bohr magneton

question: What is the unit of magentic properties of atomic nuclei?
answers: text: nuclear magneton

question: The Bohr magneton is the magnetic moment of an electron under what restriction?
answers: text: behaved as a spinning charge according to classical electrodynamics

question: What three terms define the Bohr magneton value?
answers: text: the reduced Planck constant, the elementary charge and the electron mass

question: What is the unit of magnetic properties of the neutron?

question: What is the unit of magnetic properties of nuclear molecules?

question: What three terms define the Bohr nucleus value?

question: What is never defined in terms of the reduced Planck constant?
context: The Bohr magneton and the nuclear magneton are units which are used to describe the magnetic properties of the electron and atomic nuclei respectively. The Bohr magneton is the magnetic moment which would be expected for an electron if it behaved as a spinning charge according to classical electrodynamics. It is defined in terms of the reduced Planck constant, the elementary charge and the electron mass, all of which depend on the Planck constant: the final dependence on h1/2 (r2 > 0.995) can be found by expanding the variables.

qas: question: How was the Planck constant calculated in the early 20th century?
answers: text: the Planck constant could be determined by examining the spectrum of a black-body radiator or the kinetic energy of photoelectrons

question: The value quoted here for the Planck constant is based on a measurement in what year?
answers: text: 2007

question: Where was this measurement made?
answers: text: the U.S. National Institute of Standards and Technology (NIST)

question: What method was was used to obtain the measurement?
answers: text: watt-balance measurement

question: One other measure involved the molar volume of what element?
answers: text: silicon

question: What year was the measurement for the Planck constant value avoided?

question: Where was this measurement disregarded?

question: What could be determined by examining the spectrum of a white-body radiator or the nuclear energy of photoelectrons?

question: What can never be measured with molar volume?
context: In principle, the Planck constant could be determined by examining the spectrum of a black-body radiator or the kinetic energy of photoelectrons, and this is how its value was first calculated in the early twentieth century. In practice, these are no longer the most accurate methods. The CODATA value quoted here is based on three watt-balance measurements of KJ2RK and one inter-laboratory determination of the molar volume of silicon, but is mostly determined by a 2007 watt-balance measurement made at the U.S. National Institute of Standards and Technology (NIST). Five other measurements by three different methods were initially considered, but not included in the final refinement as they were too imprecise to affect the result.

qas: question: What is a main practical difficulty in determining n?
answers: text: the two most accurate methods, the watt balance and the X-ray crystal density method, do not appear to agree with one another

question: Why does this difficulty occur?
answers: text: it is (or they are) not as precise as is currently believed

question: Which method is at fault or the discrepancy?
answers: text: there is no indication which method is at fault

question: What is a main practical difficulty in determining x?

question: Why is there no difficulty?

question: Which method is required for the discrepancy?

question: What difficulties are not involved with determining h?
context: There are both practical and theoretical difficulties in determining h. The practical difficulties can be illustrated by the fact that the two most accurate methods, the watt balance and the X-ray crystal density method, do not appear to agree with one another. The most likely reason is that the measurement uncertainty for one (or both) of the methods has been estimated too low – it is (or they are) not as precise as is currently believed – but for the time being there is no indication which method is at fault.

qas: question: Other than the X-ray crystal density method, other methods rely on what two effects?
answers: text: the Josephson effect and the quantum Hall effect

question: Why does relying on these effects create concern?
answers: text: If these theories are slightly inaccurate

question: Using Planck constant values from these effects would lead to what logical issue?
answers: text: a circular argument

question: What is the saving grace of relying on these theories?
answers: text: there are other statistical ways of testing the theories, and the theories have yet to be refuted.

question: Why is there no saving grace of relying on these theories?

question: What logical issue would using Planck constant values from these effects never lead to?

question: What theories have always been refuted?

question: What effects are never relied on?
context: The theoretical difficulties arise from the fact that all of the methods except the X-ray crystal density method rely on the theoretical basis of the Josephson effect and the quantum Hall effect. If these theories are slightly inaccurate – though there is no evidence at present to suggest they are – the methods would not give accurate values for the Planck constant. More importantly, the values of the Planck constant obtained in this way cannot be used as tests of the theories without falling into a circular argument. Fortunately, there are other statistical ways of testing the theories, and the theories have yet to be refuted.

qas: question: What is a watt balance?
answers: text: an instrument for comparing two powers, one of which is measured in SI watts and the other of which is measured in conventional electrical units

question: What value does RK represent?
answers: text: the von Klitzing constant which appears in the quantum Hall effect

question: If the effects are valid, for RK = n/e2, what is the measurement of KJ2RK equal to?
answers: text: the Planck constant

question: What does a watt balance avoid?

question: What value does RM represent?

question: What is the measurement of KJ2RR equal to?

question: What gives gives a measure of the product KJ2RR in SI units?
context: A watt balance is an instrument for comparing two powers, one of which is measured in SI watts and the other of which is measured in conventional electrical units. From the definition of the conventional watt W90, this gives a measure of the product KJ2RK in SI units, where RK is the von Klitzing constant which appears in the quantum Hall effect. If the theoretical treatments of the Josephson effect and the quantum Hall effect are valid, and in particular assuming that RK = h/e2, the measurement of KJ2RK is a direct determination of the Planck constant.

qas: question: The gyromagnetic ratio is the constant proportion between the magentic field and what?
answers: text: the frequency ν of nuclear magnetic resonance

question: How does the water molecule impact the effect of magnetic fields on protons?
answers: text: The protons are said to be "shielded" from the applied magnetic field by the electrons in the water molecule

question: What three factors impact the gyromagnetic ratio?
answers: text: related to the shielded proton magnetic moment μ′p, the spin number I (I = 1⁄2 for protons) and the reduced Planck constant.

question: The gyromagnetic ratio is often difficult to determine due to difficulty accurately determining the value of what?
answers: text: the applied magnetic field B

question: What ratio is the difference of proportionality between the frequency ν of nuclear magnetic resonance (or electron paramagnetic resonance for electrons) and the applied magnetic field?

question: What three factors impact the gyroelectric ratio?

question: What is never related to the shielded proton magnetic moment?

question: What effect is a the same effect that gives rise to chemical shift in KMR spectroscopy?
context: The gyromagnetic ratio γ is the constant of proportionality between the frequency ν of nuclear magnetic resonance (or electron paramagnetic resonance for electrons) and the applied magnetic field B: ν = γB. It is difficult to measure gyromagnetic ratios precisely because of the difficulties in precisely measuring B, but the value for protons in water at 7002298150000000000♠25 °C is known to better than one part per million. The protons are said to be "shielded" from the applied magnetic field by the electrons in the water molecule, the same effect that gives rise to chemical shift in NMR spectroscopy, and this is indicated by a prime on the symbol for the gyromagnetic ratio, γ′p. The gyromagnetic ratio is related to the shielded proton magnetic moment μ′p, the spin number I (I = 1⁄2 for protons) and the reduced Planck constant.

qas: question: How many methods of measuring the gyromagnetic ratio are there?
answers: text: there are two methods of measuring the value

question: How do conversion factors compare in "low-field" and "high-field" methods of measuring the gyromagnetic ratio?
answers: text: the conversion factors are different in the two cases

question: Which method is of interest in determining the Planck constant?
answers: text: Only the high-field value Γ′p-90(hi) is of interest in determining the Planck constant

question: Why is the measurement of electric current an issue in the estimate of the gyromagnetic ratio?
answers: text: electric current: this is invariably measured in conventional amperes rather than in SI amperes

question: How many methods of measuring the gyroelectric ratio are there?

question: How do conversion factors compare in "low-field" and "high-field" methods of measuring the gyroelectric ratio?

question: Which method is of interest in determining the Planck difference?

question: Why is the measurement of gyroelectric current an issue in the estimate of the gyromagnetic ratio?
context: A further complication is that the measurement of γ′p involves the measurement of an electric current: this is invariably measured in conventional amperes rather than in SI amperes, so a conversion factor is required. The symbol Γ′p-90 is used for the measured gyromagnetic ratio using conventional electrical units. In addition, there are two methods of measuring the value, a "low-field" method and a "high-field" method, and the conversion factors are different in the two cases. Only the high-field value Γ′p-90(hi) is of interest in determining the Planck constant.

qas: question: What is the Faraday constant?
answers: text: the charge of one mole of electrons

question: How is the Faraday constant determined?
answers: text: by careful electrolysis experiments, measuring the amount of silver dissolved from an electrode in a given time and for a given electric current.

question: How does the Faraday constant relate to the Planck constant?
answers: text: Substituting the definitions of NA and e, and converting from conventional electrical units to SI units, gives the relation to the Planck constant.

question: How is the Farday constant value quickly calculated?
answers: text: the Avogadro constant NA multiplied by the elementary charge e

question: What is the Faraday difference?

question: How is the Faraday difference determined?

question: How does the Faraday difference relate to the Planck difference?

question: How is the Farday difference value slowly calculated?
context: The Faraday constant F is the charge of one mole of electrons, equal to the Avogadro constant NA multiplied by the elementary charge e. It can be determined by careful electrolysis experiments, measuring the amount of silver dissolved from an electrode in a given time and for a given electric current. In practice, it is measured in conventional electrical units, and so given the symbol F90. Substituting the definitions of NA and e, and converting from conventional electrical units to SI units, gives the relation to the Planck constant.

qas: question: What is the primary method for determining the Avogadro constant?
answers: text: The X-ray crystal density method

question: The Avogadro constant is determined to be the ratio between what two factors in the X-ray crystal density method?
answers: text: the volume of the unit cell of a crystal, measured by X-ray crystallography, and the molar volume of the substance

question: What element is used typically to establish Avogadro's constant?
answers: text: Crystals of silicon

question: How is unit cell volume calculated?
answers: text: from the spacing between two crystal planes referred to as d220

question: Calculating molar volume requires knowledge of what two factors?
answers: text: the density of the crystal and the atomic weight of the silicon used

question: What is the secondary method for determining the Avogadro equilibrium?

question: What element is typically used to establish Avogadro's formula?

question: How is unit nucleus volume calculated?

question: What two factors of knowledge are required to calculate solar volume?

question: What is not available in high quality and purity for the semiconductor industry?
context: The X-ray crystal density method is primarily a method for determining the Avogadro constant NA but as the Avogadro constant is related to the Planck constant it also determines a value for h. The principle behind the method is to determine NA as the ratio between the volume of the unit cell of a crystal, measured by X-ray crystallography, and the molar volume of the substance. Crystals of silicon are used, as they are available in high quality and purity by the technology developed for the semiconductor industry. The unit cell volume is calculated from the spacing between two crystal planes referred to as d220. The molar volume Vm(Si) requires a knowledge of the density of the crystal and the atomic weight of the silicon used. The Planck constant is given by

qas: question: What measurement is deemed most important to redefine in terms of physical constants?
answers: text: the kilogram

question: What is the shape of the object that establishes the base unit of the kilogram?
answers: text: cylinder

question: What alloy is the base unit of the kilogram made from?
answers: text: platinum–iridium

question: Where is the base unit for the kilogram kept?
answers: text: in a vault just outside Paris

question: What measurement is deemed least important to redefine in terms of physical constants?

question: What is the shape of the object that establishes the base unit of the kilometer?

question: What value has consistently changed since 1889?

question: Where is the top unit for the kilometer kept?

question: What kind of alloy is never used to measure a kilogram?
context: There are a number of proposals to redefine certain of the SI base units in terms of fundamental physical constants. This has already been done for the metre, which is defined in terms of a fixed value of the speed of light. The most urgent unit on the list for redefinition is the kilogram, whose value has been fixed for all science (since 1889) by the mass of a small cylinder of platinum–iridium alloy kept in a vault just outside Paris. While nobody knows if the mass of the International Prototype Kilogram has changed since 1889 – the value 1 kg of its mass expressed in kilograms is by definition unchanged and therein lies one of the problems – it is known that over such a timescale the many similar Pt–Ir alloy cylinders kept in national laboratories around the world, have changed their relative mass by several tens of parts per million, however carefully they are stored, and the more so the more they have been taken out and used as mass standards. A change of several tens of micrograms in one kilogram is equivalent to the current uncertainty in the value of the Planck constant in SI units.

qas: question: Where would the decision to change the definition of the kilogram have occured at the earliest?
answers: text: the General Conference on Weights and Measures in 2011

question: Was the Planck constant the only option for redefining the kilogram?
answers: text: The Planck constant is a leading contender to form the basis of the new definition, although not the only one

question: The mass of a resting body with what energy would be equal to a kilogram?
answers: text: 7050135639273999999♠135639274×1042 Hz

question: A kilogram could be definined as having a Planck constant of what value?
answers: text: 6966662606895999999♠6.62606896×10−34 J⋅s

question: Where would the decision to change the definition of the kilometer have occured latest?

question: What is the only thing that can form the basis of the new definition?

question: When did the legal process to change the definition of the kilogram end?

question: What definition has never had anyone attempt to change it?
context: The legal process to change the definition of the kilogram is already underway, but it had been decided that no final decision would be made before the next meeting of the General Conference on Weights and Measures in 2011. (For more detailed information, see kilogram definitions.) The Planck constant is a leading contender to form the basis of the new definition, although not the only one. Possible new definitions include "the mass of a body at rest whose equivalent energy equals the energy of photons whose frequencies sum to 7050135639273999999♠135639274×1042 Hz", or simply "the kilogram is defined so that the Planck constant equals 6966662606895999999♠6.62606896×10−34 J⋅s".