1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Planck radiation law problem

  1. Sep 17, 2007 #1
    1. The problem statement, all variables and given/known data
    Deduce an approximation for Planck's radiation law: To what what wavelength does hv/kT=1

    2. Relevant equations
    Wien Distribution equation
    B(lambda)= 2hc^2/lambda^5*exp(-hc/kT(lambda))
    Rayleigh-jeans approximation
    3. The attempt at a solution
    My main concern is with the latter part of the question: To what wavelength does hv/kT=1?

    My first attempt at finding a wavelength was to equate Rayleigh-jeans approximation equations and the Wien Distribution equations to each other.

    (2hc^2/lambda^5)*exp(1/lambda) = 2ckT/lambda^4 . Then to eliminate T from the equation , I would set T= hv/k. Therefore 2ck(hv/k)/(lambda)^4 = 2hc^2/(lambda)^5*(exp(-1/lambda) => lambda=c/2/v. The only problem is , I still have an unwanted unknown, which is the frequency. Do you need the frequency in order to determine the wavelength?
  2. jcsd
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted