Question

For the Fraunhofer diffraction to occur, the wave front incident on the aperture must be?
A. Spherical
B. Plane
C. Cylindrical
D. Elliptical

Answer 1

Hint: Recall that diffraction is the process by which light seems to bend around the corners of an object and may impinge into the geometrical shadow of the object. Diffraction due to a straight edge and diffraction due to a narrow wire are examples of Fresnel diffraction, whereas Young's double slit experiment is an example of Fraunhofer diffraction.

Complete step by step answer:
Fraunhofer Diffraction

In this type of diffraction, the source of light and the screen are at an effective infinite distance from the diffracting object (i.e., the slit).
For this reason, it is called far-field diffraction.
Since the source is at an infinite distance from the slit, the incident wavefront is usually a plane wavefront.
The diffraction pattern remains the same irrespective of any shift in the object (slit) position.
The shape and intensity of the diffraction pattern remains the same throughout.
So, we can conclude that for the above Fraunhofer diffraction to occur, the wave front incident on the aperture must be Planer/plan.

Note: Fraunhofer diffraction is an example of Young’s double slit experiment.
Young's double slit experiment is when a monochromatic light passes through two narrow slits then there is formation of dark fringes and bright fringes; these fringes are caused due to the superposition of the light waves from the two slits.