Question

In case of plane diffraction grating, the incident as well as diffracted
wavefronts is
a) spherical b) cylindrical c) plane d) non-planar​

Answer 1

Answer:

c

Explanation:

This diffraction grating comes under Fraunhofer's diffraction in which incident wavefront is plane .

Answer 2

The incident and diffracted rays fall on the grating's plane side.

What is plane diffraction grating?

When a monochromatic light beam of wavelength strikes a grating, it diffracts along several discrete paths. The triangular grooves protrude from the page, while the rays lie in the plane of the page.

Incorrect options:

a) spherical

Fresnel diffraction is a type of diffraction that can be used to study the propagation of waves in the near field. Wavefronts emitted from a point source in the near field are spherical. So it cannot be considered as the plane diffraction grating.

b) cylindrical

The incident and diffracted wavefronts are cylindrical in Fresnel diffraction. The aperture's incident wavefront is also cylindrical. So it cannot be considered as the plane diffraction grating.

d) non-planar​

The variational principle is satisfied by the diffracted field in certain parts of both the near and far fields of a slit aperture formed by two non-planar screens. So it cannot be considered as the plane diffraction grating.

Hence, the correct option is c) plane denotes the plane diffraction grating, as well as the incident and diffracted wavefronts.