Write Einstein’s photoelectric equation and point out any two characteristic properties of photons on which this equation is based. Briefly explain the three observed features which can be explained by this equation. 

Einstein’s photoelectric equation is given by, 
                   

Characteristic property of photons:

i) Energy of photon is directly proportional to the frequency.

ii) Total energy and momentum of the system of two constituent particles remain constant in photon-electron collision.

Three observed features of photoelectric effect are:

i) When frequency of incident photon increases, kinetic energy of emitted electron increases. Kinetic energy does not have any effect on Intensity of radiations.

ii) When intensity of incident light increases, the number of incident photons increases. The increase in intensity will increase the number of ejected electrons. That is, photocurrent will increase with increase of intensity. Frequency has no effect on photocurrent.

iii) When the energy of incident photon is greater than work function, the photoelectron is immediately ejected. Thus, there is no time lag between incidence of light and emission of photoelectrons.