AAMC MCAT Physics Sample Section?

Question

Does anyone know the answer to the #16 on the Physics sample section? Thanks!

http://www.aamc.org/students/mcat/pssampleitems.pdf

Answer 1

First, I'm pretty sure that wavelength has nothing to do with the probability in this case because it simply corresponds with the energy of the photons.

Second, the passage indicates in the last paragraph that intensity "is proportional to the number of X-ray photons emitted at <lamda>." Since peak P2 has the higher intensity, more X-ray photons were emitted at that wavelength, so that particular emission was a more probable event.

Therefore, the answer is D.