Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

We all know that in Rayleigh-Jeans law,

$$N(f)df ~=~ 8\pi f^2 df/c^3.$$

How do you derive $N(\lambda)d\lambda$?

I am sort of confused...

share|cite|improve this question

by wave theory $ \lambda =vT $ and $ f=1/T $ the waves move to the speed of light so

$ f= \frac{c}{\lambda} $ then $ d\lambda = -\frac{cdf}{f^{2}} $ simply replace in your equation.

i believe he is referring to $ f= \nu = 2\pi \omega $

share|cite|improve this answer
I believe you mean $\omega = 2 \pi f$ – kleingordon Aug 10 '12 at 22:09
yes i tried this but made a misteake :D sorry – Jose Javier Garcia Aug 11 '12 at 8:58

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.