DIFFRACTION
When light is incident on an obstacle whose size is comparable with the wavelength of light then the
incident light bends around the edges or corners. This bending phenomenon of light is known as diffraction.
It results bright and dark shadow regions known as diffraction pattern.
It is classified into two types. They are
(1) Fresnel diffraction
(2) Fraunhofer diffraction
a) Fresnel diffraction:
In this diffraction, the source and screen are kept at finite distances from the obstacle. Hence,
lenses are not required to see the diffraction. It can be studied in the direction of propagation of light.
Here the incident wave fronts are either spherical or cylindrical.
b) Fraunhofer diffraction:
In this diffraction, the source and screen are kept at infinite distances from the obstacle. Hence,
lenses are required to see the diffraction. It can be studied in any direction. Here the incident wavefronts
are plane wavefronts.