1. The problem statement, all variables and given/known data Which of the following phenmena can be explained on the basis of the particle nature of light a. hydrogen spectrum b. spectrum by a prism. c. photoelectric effect d. x- rays 2. The attempt at a solution i know that that the photoelectric effect is a proof that light exists as photons and x- rays too are a proof of the same. But when a looked at the answer, even the hydrogen spectrum was included along with the above mentioned two. How can the hydrogen spectrum be explained on the the basis of the particle theory of light?