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**1. Homework Statement**

Deduce an approximation for Planck's radiation law: To what what wavelength does hv/kT=1

**2. Homework Equations**

Wien Distribution equation

B(lambda)= 2hc^2/lambda^5*exp(-hc/kT(lambda))

Rayleigh-jeans approximation

B(lambda)=2ckT/lambda^4

**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?