Hello, 1)I want to prove that the number of photons emitted per unit of surface of black body, per unit of time and per unit of space of frequency is: n(v,T)=(2*π*v^2)/[c^2*exp(h*v/k*T) - 1] Any ideas?! :uhh: 2)How can I find the wavelength as a function of the kinetic energy i)for photons, ii)for electrons? i)For photons. Look what I've done so far. I used the relation: E^2=c^2*p^2+(mc^2)^2 The photon's rest mass is 0. So we get: E=c*p p=E/c ---> p=h*v/c --->p=h/λ Finally: λ=c*h/E ii)For electrons. I don't know what to do Do you think that I should use the photoelectric equation (E=h*v - W)??? I appreciate any help. Thank you.