Write the important properties of photons …

The energy of the electrons does NOT depend on the intensity of the light. Each electron absorbs only one photon at a time. If the absorbed energy is large enough to expel the electron from the metal, it leaves. If not, the electron dissipates its energy in collisions with nearby electrons and atoms before it can absorb another photon. And yes, this implies that the time it takes for an electron to lose the energy gained in one absorption is much smaller than the interval between absorptions. Under ordinary circumstances, it is. The electrons always appear AS SOON AS the light reaches the plate (though a feeble light produces only a few). As soon as a single photon containing sufficient energy strikes the source plate, it will knock an electron free. There is no need to wait for multiple waves to build up enough energy. NO electrons are produced if the frequency of the light waves is below a critical value. Since the energy of each photon is e=hv below some critical frequency, no photon has enough energy to knock an electron free.

Travel with speed of light Electrically neutral Zero rest mass