Need A little Help With Optical Depth

[O-r-i-o-n]

Hi Everyone!
I was wondering if someone could help me with Optical Depth, I read some articles about it but since my English isn't that good I couldn't Get it well! I have some views about the Opacity But when it comes to optical depth I'll get lost :D
help!

[malawi_glenn]

This contains everything you need basically;)

"RADIATIVE TRANSFER
IN
STELLAR ATMOSPHERES"

http://www.astro.uu.nl/~rutten/rrweb/rjr-material/masters/rtsa/afy.pdf


It is better with precisie questions, how are we supposed to help you if we dont know what you are struggeling with? And if your english is not that good, improve it, "everything" is written in english.

[O-r-i-o-n]

275 pages? what would you have sent me if I had said my English is good? :D
Thanks man but I needed sth simpler , sthh in high school level (or a little higher)

[cadnr]

Try this:

http://scienceworld.wolfram.com/physics/OpticalDepth.html

[O-r-i-o-n]

Already read that one , but thanks! I got somethings from that!

[malawi_glenn]

but its not all 275 pages.. just read the section about optical depth!!!

and try here: http://en.wikipedia.org/wiki/Optical_depth

Can you try to specify your question?

[O-r-i-o-n]

I don't have a specific question about Optical Depth , I just want to know what it is and what are it's uses and why astronomers use it. and about the 275 pages , really? because the number freaked me out so I didn't go to the details :D , thanks I'll check it out

[malawi_glenn]

its not only about optical depth, it is about radiative transfer. Why didnt you read the table of contents? First part of chapter 2 introduces optical depth etc.

[cadnr]

It's basically just a measure of how opaque a given path is to radiation. Optical depth is proportional to the number of (light-absorbing) particles along a given line of sight, so it's a very useful quantity in astronomy when it comes to working out the amounts of atoms or molecules in different gases you're looking through.

[AstroRoyale]

The optical depth related to the probability of escape of a photon travelling trough a medium. The probability for a photon to escape is e^(-tau), where tau is the optical depth (and is a function of wavelength or frequency).

[O-r-i-o-n]

Thank you all! Got what I needed!