P.S. In many books, light ray is coming from the outside of the elevator cabin. In some books, light source is set on the wall of the cabin. In the former, falling of the cabin will have no effect on light ray (imagine a cabin without wall). In the latter (if the emission theory is true), behavior of light ray will be easy to imagine.
For a 10 seconds, an elevator cabin accelerated upward and stopped. Number of waves of light that appears and vanishes during that time will be the same.
