Question

In Fresnel diffraction, the incident wavefront is either:
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Answer 1

Answer:

Fresnel diffraction : when the light source and the observation point are at finite distance from the obstacle , diffraction so produced, is called Fresnel diffraction. In this diffraction the incident and the diffracted wave front are spherical or cylindrical.

Answer 2

Spherical or cylindrical.

• In Fresnel Diffraction, the interference takes place between the light waves reaching a point from different parts of the same wavefront.
• Therefore the incident wavefront is spherical or cylindrical.
• In Fresnel diffraction, the source of light and the screen are at a finite distance.
• The diffracting aperture or obstacle has sharp edges.
• The diffraction phenomena are divided into two classes:

             (i) Fresnel diffraction and

             (ii) Fraunhofer diffraction.

Hence, we conclude that In Fresnel diffraction, the incident wavefront is either spherical or cylindrical.