Why does zinc sulfide glow when hit by electrons? In cathode ray tube experiment in order to check the direction of flow of electrons a hole was made in a note and behind it phosphorescent material zinc sulfide it was coated.

Why does zinc sulfide glow when hit by electrons?
What causes this glow?
This is an example of phosphorescence. The Wikipedia page of zinc sulfide and phosphorescence can explain it better than I do, but in short, when zinc sulfide get hit by electrons, electrons transfer some of its energy to zinc sulfide and excites its electron. Zinc sulfide stores the energy for a while, then emit light when the electron goes back to its ground level.