Question

Photoelectric effect supports quantum nature of light because:
A. There is a minimum frequency of light below which no photoelectrons are emitted.
B. The maximum kinetic energy of the photoelectrons depends only on the frequency of the light and not on its intensity.
C. Even when the metal surface is faintly illuminated, the photo electrons leave the surface immediately.
D. Electric charge of the photo electrons is quantized.

Answer 1

Hint: Photocurrent is the current produced when light falls on a photo diode or a metal with suitable work function. Work function is defined as the minimum energy required to eject an electron from the surface of the material. It also corresponds to the minimum frequency, the photon of which when falls on the surface of a metal, the photoelectron gets ejected. This phenomenon of ejection of an electron is known as photoelectric effect.

Complete answer:
Light is believed to have dual behavior: wave and particle. Some properties of light could be explained by using wave nature and some are explained by using the particle nature of the light. For instance, the photoelectric phenomenon is explained by using particle nature or quantum nature of light.
Photoelectric effect cannot be explained on the basis of wave nature because experimentally we know that we need a particular energy called the work function of the metal surface. Also, the frequency of photons corresponding to this value of work function is called threshold frequency. Unless this energy is provided, the electron won’t be ejected, irrespective of the time for which light is incident. Hence photoelectric emission is independent of intensity. But if light were a wave, which is a continuous source of energy, we must get electrons if energy is less that work function, if light is incident for a larger time! Which is not the case!
Hence, the kinetic energy is also independent of the intensity of light incident and depends only upon the frequency of coming light. Also, when the frequency is sufficient to eject the electron, the electron gets ejected from the surface quickly and it could be analogous with a ball (moving photon) colliding with another ball (electron).

So, the correct answer is “Option A,B and C”.

Note:
Photons possess mass only when in motion. Hence it has definite kinetic energy and momentum as well only when it is in motion. Hence when a moving photon is struck a surface, it transfers all its momentum to the electrons resulting in photoemission.