What is photon wavelength?!!! What is photon wavelength exactly? I know that the energy of a photon is E = hc/lambda, where frequency = c/lambda and lambda is the wavelength. So, what determines the wavelength of a photon? Is it the distance an electron falls from the conduction band back down to the valence band?? Also, is it incorrect to visualize an electron's frequency as vibration or rotation?? It is difficult to visualize what the frequency of a photon is if it correlates to speed and distance... Thank you.