Talk:Beer–Lambert law

message: "...relates the attenuation of light to the properties of the material through which one substance like light, neutrons or host rarefied gases is traveling"
Is light now a substance?  
It's not clear what the defining characteristics are of the class "substance like light, neutrons or host rarefied gases".  Would whey (traveling through cheesecloth) count?   
So if you have neutrons passing through a material, light is attenuated?  What light is affected?
I realize that it's difficult to explain highly technical subjects to fourth-graders, but it would make this highly important page MUCH more useful if was written clearly, instead of simply tossing keywords on the page, without bothering to ensure the sentences make sense.12.193.238.99 (talk) 23:08, 20 September 2014 (UTC)
replies: text: I agree with the concerns expressed that the introduction had become needlessly convoluted. Concepts were introduced that were never developed further. Advanced concepts were included that were confusing. I have edited the introduction with the goal of highlighting the key elements. A note to the commenter, all users are welcome to edit Wikipedia, and your insights were valuable, so I suggest you follow through and give editing a try. ronningt (talk) 00:39, 22 September 2014 (UTC)
thread_title: Howzat Again?

message: *Equations:"The frequency scale in molecular spectroscopy is often in cm-1, wherefore the lineshape function is expressed in units of 1/cm-1, which can look funny but is strictly correct." Correct me if I am wrong, but doesn't 1/cm-1 just equal cm? Kbw1988 (talk) 12:43, 15 May 2008 (UTC)
replies: text: Dimensional analysis agrees with you, but perhaps there is some other error.--Srleffler 05:24, 16 February 2006 (UTC)
thread_title: Comments

message: Am I the only one who feels the picture is unsuitable? The rhodamine is fluorescing - the light that is diminishing with greater pathlength is not the incident beam but light arising from the absorption of the incident beam.  that's adding a whole new layer of confusion - could someone post a  similar picture with a non-fluorescing material? Or a picture of a pane of glass from the from and side, showing how the increased pathlength leads to increased absorption resulting in the glass looking green from the side  — Preceding unsigned comment added by 86.46.54.236 (talk) 16:30, 6 July 2012 (UTC)
thread_title: Picture

message: I think the article should more explicity explain the relationship beween absorbance and transmittance, or point to an article that does cover this.  It is sort of in the article already (Ii/Io), but that wouldn't be clear to the uninitiated. ike9898 17:43, 14 March 2006 (UTC)
thread_title:  Transmittance 

message: Precise references are needed to back up the history section, particularly with regards the role of Bouguer. Ga2re2t 17:00, 25 October 2007 (UTC)
thread_title:  History 

message: I found the equation  \alpha = \frac{4\pi k}{\lambda} (4th equation from this article) to be confusing
I reasoned, since alpha has various sets of units (see paragraph below) so must k, yet the way k is derived in the article Extinction coefficient indicates that k has only one set of units, and if the equation above is correct alpha must have only one set of units, which comes back to my point that I am confused.
So I wanted to ask/plead that someone who knows whats going on, amend either the paragraph below quoted from the article or the equations, such that the whole thing is less confusing. Or at least so that the units for the equation \alpha = \frac{4\pi k}{\lambda} are clear.
"The units of c and α depend on the way that the concentration of the absorber is being expressed. If the material is a liquid, it is usual to express the absorber concentration c as a mole fraction i.e. a dimensionless fraction. The units of α are thus reciprocal length (e.g. cm−1). In the case of a gas, c may be expressed as a density (units of reciprocal length cubed, e.g. cm−3), in which case α is an absorption cross-section and has units of length squared (e.g. cm2). If concentration c is expressed in moles per unit volume, α is a molar absorptivity (usually given the symbol ε) in units of mol−1 cm−2 or sometimes L mol−1 cm−1." — Preceding unsigned comment added by 139.67.205.181 (talk) 
: I think it is ok to have multiple units for \alpha and c but only one unit for k. The reason being that the if you use the equation \alpha = \frac{4\pi k}{\lambda} to relate \alpha and k, then \alpha will be in units of cm-1 (or L-1) and correspondingly the concentration c will have to be expressed in mole fraction. However, for a given substance, the concentration can be expressed in other units by using appropriate constants. for example, it is common to refer to both frequency ( f ) and angular frequency ( \omega ) as frequency, even though they have different units (Hz) and (rad/s) respectively. The two can be readily interchanged by noting that \omega = 2 \pi f. Anyhow, I will try to fix the statement soon, so that it is not confusing. Thanks for the comment. -Myth (Talk) 05:30, 9 February 2007 (UTC)
thread_title:  Relationship of k to alpha 

message: Something is wrong with the first section (2007-03-22).  There's a missing ln(10) somewhere.  This is obvious, since A is defined in terms of log10, but the rest of the constants are non-log quantities.  I'm not sure where it goes, though. —The preceding unsigned comment was added by 192.249.47.9 (talk) 19:04, 22 March 2007 (UTC)
thread_title:  Something wrong with alpha 

message: IUPAC recommends that ε be called the molar (decadic) absorption coefficient.  See , , and especially .
— DIV (128.250.204.118 08:20, 7 September 2007 (UTC)
thread_title:  Molar (decadic) absorption coefficient 

message: I am under the impression that absorptivity should not redirect to this page.
Absorptivity, as it pertains to heat transfer and infrared radiation/optics, is a simple ratio of the irradiation absorbed over the total irradiation. Where, the total irradiation is the radiative flux incident to a surface, both from direction emmission and reflection from all other surfaces in a system. Additionally this unit is dimenssionless and is also given by the greek letter alpha.
The strict definition of absorptivity in infrared radiation is completely analagous to reflectivity and the emissivity.
Furthermore, several wikipedia pages reference and link to this page on absorptivity  however they are obviously refering to the dimensionless absorptivity and not to the absorbance that this article discusses.
I could and probably will fix this inconsistency, by the end of the year hopefully, with the addition of a start up article on absorbtivity.
I would appreciate feed back on the discussion page or my talk page. 
The Lamb of God (talk) 16:32, 17 June 2009 (UTC)
replies: text: Absorptivity is equal to emissivity, right? So maybe it should redirect there.... (Of course, that page would require some additional text explaining it.) --Steve (talk) 22:00, 17 June 2009 (UTC)
thread_title:  Absorptivity redirect 

message: This article is ridiculously verbose.  There are way too many examples, at most one example is needed.  In particular the "Chemical Analysis" and "Beer–Lambert law in the atmosphere" sections could simply be deleted.  The discussion about different units is unimportant to a general audience.  (As a matter of fact, it can be highly confusing to specialists.)
:I completely disagree  —Preceding unsigned comment added by 128.120.188.230 (talk) 04:19, 4 December 2009 (UTC)
thread_title:  Verbosity 

message: I've tried googling for it (define: aborbance) and I've tried m-w.com--neither one defines it.  If I search for aborbance, I find  lots of references to it (over a 1000, iirc), but my guess they are all careless misspellings.
I was going to correct the spelling, but I have just a little bit of doubt.  (If someone does correct it, search the page, I think there is more than one occurrence.)
Rhkramer (talk) 11:40, 2 November 2010 (UTC)
thread_title:  Is aborbance a word? 

message: I'm a third year pharmacy student, and I've done my first year of basic chemistry, and even I find it difficult to follow this page. I can't imagine how this looks to person with a non-science background. I of all people understand the need to explain things properly, but this page seriously needs to be simplified somehow. I've not seen anything resembling "A = ε b c", nor do I think I have seen a mentione of ε1%. Seriously, please do something about this Chairman Xi (talk) 05:31, 10 March 2012 (UTC)
replies: text: Yep, totally agree with you. The article is WAY too complicated. 2A02:8388:1603:CB00:3AD5:47FF:FE18:CC7F (talk) 11:58, 10 December 2017 (UTC)
thread_title:  Water it down a bit maybe? 

message: It is implicit in the law that shadowing must occur. This is because the incident intensity on the infinitesimally thin slab is dependent on the output intensity of the slab before. If no shadowing occurred, there would be no need to perform calculus and the entire slab would be considered as one. Putting this falsehood back in the article is lying to people. If you think better wording should be used, then try to word it better, but leave in the fact that the shadowing is required for the derivation of the law to hold true (which actually means the law breaks down at low concentration/pathlength/extinction coefficient) not high).Black.jeff (talk) 20:30, 17 October 2013 (UTC)
replies: text: Shadowing is a concept which makes only sense in ray optics. Beer's law requires that absorbers are small compared to the wavelength, which means it belongs to the domain of wave optics. In wave optics the concept of shadowing breaks down... — Preceding unsigned comment added by Beenhereb4 (talk • contribs) 11:25, 26 May 2019 (UTC)
thread_title:  Shadowing & law breakdown. 

message: I would like to point out that an editor of the French article has deleted the section on the atmosphere as "totalement faux" (totally false). When I asked for further explanation on the talk page, that editor and one other explained that the equation given does not apply to diffusive media such as the atmosphere. See discussion in French at :fr:Discussion:Loi de Beer-Lambert#Suppression de section Loi de Beer-Lambert dans l'atmosphère.
This raises the question of whether the section should be removed from the English article also. I don't know enough to judge whether the objections are valid. Perhaps those editors who are more expert in optical theory could read the French discussion and comment. Dirac66 (talk) 00:59, 31 December 2016 (UTC)
thread_title:  Validity of atmospheric section questioned 

message: I ended up watching some youtube videos explaining the law, which is a LOT simpler than the whole article there.
I have no problem with anyone explaining things in a complicated way per se, but wikipedia should also teach people; and from this point of view, the article is worded and structured in a WAY too complicated manner. Not everyone is a maths genius - the article was clearly written by physicists mostly. 2A02:8388:1603:CB00:3AD5:47FF:FE18:CC7F (talk) 11:57, 10 December 2017 (UTC)
thread_title:  Difficult article 

message: It occurred to me answering a question on Mass attenuation coefficient related to lambda, that lambda is commonly used for absorption coefficients (in the numerator of the exponent), though not in this article. (Maybe more in physics, and less chemistry.) I then noticed the similarity between lambda and Lambert, and (without doing any actual WP:OR) that they might be related. On the other hand, there are only so many letters, and after a while some do get reused. Gah4 (talk) 21:50, 17 February 2022 (UTC)
thread_title:  Lambda 

message: I looked at the comments and gave it my best shot.  I tried to include references in what I wrote, but did not look for them in the math section.  A major facto is that Beer's law has come to mean much more than the relatively straight forward use in Chemical Spectroscopy.  I tried to enlarge the scope rather than restrict the article to the tem in the title. 
Sometime, someone should include illustrations. DJDahm (talk) 14:21, 17 May 2023 (UTC)
thread_title:  Rewrite of Non-Math sections 

message: Quite the contrary. Taken from Beer's paper: "Ist der hieraus sich ergebende Schwächungs - Coefficient λ, so hat er für eine doppelte Dicke den Werth λ^2. Bei der doppelten Dicke wird aber ebenso viel concentrirte Lösung durchstrahlt, als bei der Dicke eines Decimeters und der Verdünnung 1/9." In other words, concentration × path length = const.  Beenhereb4 (talk) 18:06, 5 May 2024 (UTC)
thread_title:   There is no evidence that Beer saw concentration and path length as symmetrical variables in an equation in the manner of the Beer-Lambert law.