Einstein wins a Nobel Prize for physics in 1922, but not for his theory on relativity. For what work is he given the Nobel, and why is relativity not included?

At this point in time, Einstein's theory on relativity is still hotly disputed. The committee in charge of deciding prize winners thinks that it is too early to award him the Nobel for that work, as the true value of the theory is not yet known. Instead, he is awarded the Nobel for his work on photoelectric law and theoretical physics.