Prove Attenuation Length = Avg Photon Travel Distance

  • Thread starter Thread starter strangequark
  • Start date Start date
  • Tags Tags
    Attenuation Length
Click For Summary
SUMMARY

The discussion centers on proving that the attenuation length, denoted as \(\Lambda\), is equal to the average distance a photon travels before being scattered or absorbed. The key equations provided include the number of photons absorbed, represented as \(\sigma \rho I(x) dx\), and the intensity after a thickness \(x\), given by \(I(x) = I(0)e^{-\sigma \rho x}\). The attenuation length is defined as \(\Lambda = \frac{1}{\sigma \rho}\). The average distance traveled by photons is expressed through the integral \(x_{avg} = \int^{\infty}_{0} x \sigma \rho e^{-\sigma \rho x} dx\).

PREREQUISITES
  • Understanding of photon scattering and absorption processes
  • Familiarity with the concepts of attenuation length and optical density
  • Knowledge of integral calculus, specifically evaluating improper integrals
  • Basic grasp of exponential functions and their applications in physics
NEXT STEPS
  • Study the derivation of the exponential attenuation law in photon transport
  • Learn about the physical significance of the cross-section \(\sigma\) in scattering processes
  • Explore applications of attenuation length in materials science and radiation physics
  • Investigate numerical methods for evaluating integrals involving exponential functions
USEFUL FOR

Students and educators in physics, particularly those focusing on quantum mechanics and photonics, as well as researchers involved in material science and radiation studies.

strangequark
Messages
37
Reaction score
0

Homework Statement



Show that the attenuation length, [tex]\Lambda[/tex], is just equal to the average distance a photon travels before being scattered or absorbed.

Homework Equations



my book gives:

number of photons absorbed = [tex]\sigma\rho I(x) dx[/tex]

number of photons present after a thickness x = [tex]I(x)=I(0)e^{-\sigma \rho x}[/tex]

attenuation length = [tex]\Lambda = \frac{1}{\sigma\rho}[/tex]

The Attempt at a Solution



i'm really not sure where to go here... some idea on how to get started would be very much appreciated... thanks
 
Last edited:
Physics news on Phys.org
ok, nevermind, I think I got it...

[tex]x_{avg}=\int^{\infty}_{0}x \sigma \rho e^{\sigma \rho} dx[/tex]

(i think)
 

Similar threads

  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
Replies
1
Views
2K
Replies
2
Views
2K
  • · Replies 1 ·
Replies
1
Views
3K
Replies
15
Views
3K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 10 ·
Replies
10
Views
22K
  • · Replies 29 ·
Replies
29
Views
4K