I always had a doubt with respect to photoelectric effect. We assume that only one photon strikes an electron. Why can't there be a case where two or more photons strike an electron at the same time thus giving away all its energy to the electron. Now if the energy of a single photon isn't enough for the electron overcome the surface potential and if energy from 2 photons( on addition) is enough, then the electron should be liberated. I believe this should be possible if a very very high intensity light is used.

Also whats the time it takes for the energy transfer from photon and electron( there must a very small amount of time atleast)?

Waiting for your reply,