Question

Distinguish between interference and diffraction.

Answer 1

Hint: Diffraction is the bending of the waves around obstacles. Interference is the superposition of waves starting from different wave fronts. Diffraction is due to the superposition of secondary wavelets from different parts of the same wave front whereas interference is the superposition of waves with different wave trains from two coherent sources.
Complete step by step answer
Light is a transverse electromagnetic wave. Diffraction and interference are phenomena observed with all waves. Interference of an electromagnetic wave is due to the superposition of two or more individual wave fronts .The fringes formed in an interference pattern are equally spaced with every bright fringes having the same intensity. Compared to diffraction a large number of fringes are formed.
The fringes formed in the case of diffraction are not equally spaced. In case of diffraction the intensity of the fringes formed decreases rapidly. Thus the central fringe has maximum intensity.
Additional Information
The Huygens-Fresnel principle .The principle states that every point on a wave front is a source of wavelets. These wavelets spread out in the forward direction, at the same speed as the source wave.


Example: When Huygens – Fresnel principle is applied on a straight wave front, each point emits a semicircular wavelet. The tangent to all the wavelets is the new wave front.
Coherent sources - two waves having the same frequency and waveform. They also have a constant phase difference which does not vary with time.

Note: Diffraction grating: It is an optical element that divides light composed of different wavelengths. When white light enters the grating, the light components are diffracted at angles that are determined by the respective wavelengths (diffraction).It uses the principle of diffraction. Similarly interference has many applications .Space applications like Radio astronomy, Measuring light intensity, retrieving images from the telescopes etc. are based on the principle of interference.