Question

What is diffraction of light? Explain its two types.

Answer 1

Hint: Diffraction of light is caused when light passes through the edges of an obstacle or a narrow slit/ opening. Around the edges like this, light bends and creates a fringed pattern. Diffraction can be classified into two types depending on the distance of the source of light and the screen where the fringed pattern forms.

Complete Answer:
Diffraction is the phenomenon where a beam of light bends when it passes through a narrow slit or through the edges of an obstacle. In doing so, the light also spreads to the areas where the geometrical shadow of the object forms.
As the wave of light shifts due to the obstacle, it gains a path difference. This causes the wave of light to interfere with itself. This interference creates a fringed pattern on a screen which consists of dark and bright fringes. The pattern formed by the fringes varies with the shape of the obstacle.
Diffraction is categorized into two types, which are-
-Fraunhofer Diffraction: In the Fraunhofer diffraction, the source of light and the screen where the diffraction pattern is observed is at infinite distance from the diffracting system.
A plane wavefront of light is considered in the Fraunhofer diffraction. And the diffraction pattern can be obtained on a screen by using a convex lens for converging. It occurs on flat surfaces.
-Fresnel Diffraction: In the Fresnel diffraction, the source of light and the screen where the diffraction pattern is observed is at a finite distance from the diffracting system. A spherical or cylindrical wavefront of light is considered for Fresnel Diffraction. It occurs on spherical phases and the pattern can be obtained on a screen by placing it at a specific distance.

Note:
For diffraction to occur properly, the size of the obstacle or the aperture must be in the same order or size as the wavelength of the light that is used for diffraction as bigger objects do not produce a significant diffraction pattern.