Question

Fresnel's type diffraction is observed when_
(A) Only screen is placed at finite distance
(B) Only source is placed at finite distance
(C) Both source and sereen are at finite distance
(D) Neither source nor screen is at finite distance​

Answer 1

Answer:

answer C is correct

Explanation:

Fresnel diffraction is a near field effect in which the screen is at a finite distance

from the diffracting device.

Answer 2

Answer:

The correct answer is C) Both the source and the screen are placed at a finite distance.

Explanation:

• Fresnel diffraction is a type of diffraction where the incident wave or exit wave cannot be viewed as a plane wave because either the electron source or the observation point, or both, are positioned at a finite distance from the object.
• By slightly adjusting the focus of the objective lens, the Fresnel diffraction phenomena can be seen as an interference fringe (Fresnel fringe) that appears in the shadow part of the object.
• Huygen's Principle states that as a wave from a single source travels through space, each wavefront can be considered to be made up of several separate secondary wavefronts.
• When a wave is obstructed, some of the secondary wavelets change in phase or amplitude, interfering with the rest of the wave that isn't affected (the rest of the secondary wavelets).
• The wave is diffracted as a result of the various interference patterns this creates.

Fresnel's diffraction is seen when both the source and the screen are at finite distances.

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