Question

For Fresnel half period zones:
(A) The amplitude of disturbance is directly proportional to the area of the zone.
(B) The radii of half period zones are directly proportional to the square root of the natural number.
(C) The area of each zone is directly proportional to the wavelength of the light.
(D) The radii of half period zones are directly proportional to the square root of the wavelength of the light.
Choose the correct answer from the options given below:

• A. (A), (B), and (C) only
• B. (B), (C), and (D) only
• C. (A), (B), (C), and (D) only
• D. (A), (C), and (D) only

Hint:

Understanding the contributions of different zones helps in designing lenses and understanding diffraction effects in various media.

Answer 1

The Correct Option is D

Fresnel half period zones are used to describe the contribution of different portions of a wavefront to the intensity at a point in the wave’s path. Each successive zone contributes an equal phase shift but alternates in sign, effectively contributing to the constructive and destructive interference pattern:
- (A) True, as the amplitude of the disturbance from each zone is a function of its area.
- (B) True, as each zone’s radius increases with the square root of its order number.
- (C) True, the area and thus the impact of each zone varies with wavelength, affecting how the wavefront constructs or destructs at a point.
- (D) True, The radii of half period zones are directly proportional to the square root of the wavelength of the light.