Question

If a photon of energy E ejects electrons from a metal with kinetic energy KE, then a photon with energy E/2.

Why the answer is "it might not eject any electrons?"

Answer 1

According to the photoelectron effect principles,

the photon energy must be enough to remove the electron which is like the threshold energy required for the effect to happen.

Now the photon with energy E is able to eject electrons and also impart them a non-zero kinetic energy KE

Now since we do not know the magnitude of KE, and the work function and threshold .!!!

so when we reduce the photons energy by half it is very less likely that electrons can be produced in the first place.o