Talk:Optical depth

message: There is a disparity here... I think an optical depth is something like transmission=exp(-depth). But I'm not sure. William M. Connolley 19:54, 1 January 2006 (UTC)
thread_title: Untitled

message: The optical depth tau is related to the fraction of light scattered.  The following equation expresses this relationship:
I/I_0= exp{-tau},
where I_0 is the incident light and I is the light that passes through the medium without being scattered.  Equivalently, for a homogenous medium, tau is the ratio of the path length to the mean free path.
Corrected definition inserted in the article, some inexactitudes corrected, some concepts in atmospheric science added. I hope it is appreciated.Marenco 26 September 2006 (UTC)
:Great! that's cleared up the definition finally. Deuar 20:13, 27 September 2006 (UTC)
thread_title:  corrected definition 

message: I think there is a cognitive problem here. As I understand it, optical depth is a property of the material you are looking through, not of you the observer or the object you are observing. However, the article talks about it in analogy to taking an object and moving it backward, which makes it sound like the medium is not what is being described by optical depth.
It might be better to speak of optical depth increasing as the fog gets thicker, and the value of optical depth being the farthest thing you can see through that fog.
Raddick 20:10, 4 November 2007 (UTC)
thread_title:  Cognitive problem with explanation 

message: For what it's worth: optical thickness (depth, whatever) is an important concept in understanding the design of thermonuclear weapons.
Basesurge (talk) 07:41, 22 March 2010 (UTC)
thread_title: Nuclear Trivia

message: Is there no difference between the 2 concepts in English stellar physics ? I can't be sure this is a mistake, I am neither an English native-speaker nor a  stellar physicist, so... Anyway, French physicists would see a big difference between optical depth (profondeur optique) and optical thickness (épaisseur optique), although the terms are often subject to confusion and related mistakes. In stellar physics :
*Optical depth deals with intensity of light generally emitted by a star,
*Optical thickness deals with transparency of a sheet of material.
Same in English ? Should it be clearly mentioned both here (the article I have been partially translating) and in Optical depth ?
Mianreg (talk) 02:39, 25 August 2010 (UTC)
thread_title: Optical Depth/Optical thickness

message: The camera aperture is obviously of practical concern. We could always choose an aperture so small that the measurements become diffraction limited, or so large that most of the scattering is not observed. But that does not invalidate the definition. Think of optical depth as a way to compare two similar things. As long as the physical setups are similar the results can be compared. However, comparing camera one with camera two or three is of little value. 
The equations in the article are significantly simplified verses those given by wolfram and other references. The definition specifically uses the word "normal" to indicate the radiation path and a camera (in fact, any sensor) can only approximate "normal". (Well, a telescope looking at the Sun is a pretty good approximation. A spectrophotometer in the lab, not so much.) Also, the actual definition of optical depth is actually an integral which, at least to me, appears to cover most of your concerns. However, I think that that is too much detail for a general audience.
You have presented some very interesting points, but I still don't understand why this bothers you. Q Science (talk) 16:42, 20 October 2010 (UTC)
thread_title: break

message: If optical depth uses the natural logarithm, e.g., rather than base 10 or 2, then the article should say so, yes?  67.248.149.19 (talk) 02:07, 14 February 2012 (UTC)
replies: text: The equations already make that clear. Q Science (talk) 04:23, 14 February 2012 (UTC)
thread_title:  Base of logarithm 

message: Inexpertly, an electric dipole moment has the units of "charge × distance", and reflects a separation of positive & negative charges, which are then further separatable, by incident EM radiations.  I.e. the dipole moment is like a gap between the nucleus & core electrons (net positive charge) and the absorbing electron (negative charge) which can be wedged wider, by an incident photon.  A correct & clear physical explanation, for the terms in the optical depth formula, could help improve the article. 66.235.38.214 (talk) 00:02, 13 November 2012 (UTC)
thread_title:  meaning of dipole moment in equation for optical depth ? 

message: At the temperature at optical depth 2/3, the energy emitted by the star (the original derivation is for the Sun) matches the observed total energy emitted.
Does this mean:
The energy emitted by a given star can be computed by replacing the star by a black body with surface temperature and radius corresponding to an optical depth of 2/3 for the star ?
178.38.105.43 (talk) 17:27, 9 April 2015 (UTC)
thread_title:  Clarify this 

message: Why is there so much italicization? What style guide does that follow? —Ben Brockert (42) 12:51, 12 June 2018 (UTC)
replies: text: Agree there is too much use of italics, the majority of terms do not require emphasis, so I took the liberty of removing most italicization. D'Lemelo (talk) 10:14, 22 September 2021 (UTC)
thread_title:  Style