Question

Which of the following phenomena works on the particle nature of light?
A.) Interference
B.) Diffraction
C.) Polarisation
D.) Photoelectric effect

Answer 1

Hint: Light can behave both as a wave and a particle. The particle nature of light means that in a certain phenomenon, the light behaves as a particle. It interacts with matter through the quanta of light called photons.

Complete step-by-step answer:
When we talk about light, we consider it as a wave having crests and troughs. Many experiments verify this wave nature of light. In those experiments like interference, diffraction and polarisation, we have a wave of light which mixes with other waves to produce constructive or destructive interference as in the case of interference and diffraction or the vibrations of the transverse along certain directions can be restricted like in the case of polarisation.

But in the photoelectric effect, something different happens. In the photoelectric effect, we have a source of light which makes an incident on a metal surface. As the light falls on the metal, electrons are ejected from the surface of the metal. This phenomena cannot be explained by the wave nature of light.

It is observed that if we increase the intensity of light then there is no change in the kinetic energy of electrons, only the number of electrons being emitted increases. But if we change the frequency of light, it should not make a difference if we consider the wave nature of light but it is observed that energy of the emitted electrons increases. Einstein explained these observations by saying that light comes in packets of energy called quanta. This quanta is called a photon which is a particle with zero rest mass. This experiment verifies the particle nature of light.

Note: It should be noted that though light has the dual nature of being a wave and a particle, these natures are never observed together. Light either acts as a particle in an experiment or a wave which can be explained using quantum mechanics only.