Question

The dual nature of light is exhibited by-

A. Photoelectric effect

B. Refraction and interference

C. Diffraction and reflection

D. Diffraction and photoelectric effect

Answer 1

Hint: Light is an electromagnetic wave, therefore, it does not require a medium to travel. We know that light is made up of waves of different wavelengths but in many cases it also exhibits particle nature, this means it is composed of particles carrying energy called photons.  

Complete solution:

Light is made up of electromagnetic waves of different wavelengths. But not only does light show wave nature, it exhibits particle nature by many of its properties. When electromagnetic radiation like light hits a material, then electrons are emitted out. It shows the particle nature of light, as the number of electrons emitted depends on the frequency of light and not the intensity. Light contains energy particles called photons which collide with the electron and transfer energy, if the energy is more than the threshold energy, electrons are emitted out.

When light travels from one medium to the other, it tends to deviate from its original path, this phenomenon is called refraction. When Light travels from a rarer medium to a denser medium, it bends towards the normal, when it travels from a denser medium to rarer medium, it bends away from the normal. By Huygens principle refraction shows the wave nature of light.

Interference is the phenomenon in which light waves from two coherent sources interfere with each other or superimpose to form a resultant wave which results in the formation of bright or dark fringes. Interference shows the wave nature of light. Diffraction is the phenomenon in which light bends around an obstacle or particle in its path which leads to the spreading of the waves. Diffraction shows the wave nature of light.

Reflection is the phenomenon of bouncing back of light after striking a smooth polished surface in such a way that it obeys the laws of reflection at all times. By Huygens principle, reflection shows the wave nature of light. Therefore, the photoelectric effect shows the particle nature of light while diffraction shows the wave nature of light.

Hence, the correct option is D.

Note:

 Threshold energy is the minimum energy required by an electron to leave its orbit and emit out in photoelectric effect. According to Huygen's principle every point on a wave acts as new sources of wavelets which expand in every direction. Coherent sources are those sources which have the same phase or a constant phase difference.