A photocell is based upon the photoelectric effect. A light beam illuminates a metallic plate, and under certain conditions electrons are ejected from the metal. In order to measure the maximum kinetic energy of the electrons, another plate is kept at a negative enough potential that the emitted electrons are slowed down and stopped. Explain how the particle-like aspect of light can explain the following:
(i) the absence of delay in the observation of current,
(ii) the existence of a cut-off frequency which is independent of the intensity of light,
(iii) the fact that the maximum kinetic energy of the electrons only depends on the frequency, not the intensity.

i) photons, they collide with the electrons

ii)when the energy of the photons is less than the work function there is no way to get out electrons

iii) he energy depends on the frequency in this Planck postulate

Explanation:

This exercise the photo cell is used for the photoelectric effect, this effect was explained by Einstein

i)  Where the light is supposed to act as a particular, therefore, it is called photons, they collide with the electrons and they can tear off the metal, with a collision it is very fast there is no measurable wait in the process.

ii) since we have a shock process, the equation must be fulfilled

          K = h f - Ф

where E = h f is the energy postulated by Plank and Ф the work function of the metal, therefore when the energy of the photons is less than the work function there is no way to get out electrons, which determines a threshold energy in the process

iii) From the same previous equation, the energy depends on the frequency in this Planck postulate, and not on the intensity squared as accepted in classical mechanics.

less than one you can't create energy