Fresnel diffraction is produced due to light rays falling on a small obstacle. The intensity of light at a point on a screen beyond an obstacle depends on

Explanation

The image depicts Fresnel diffraction, which occurs when light diffracts around the edges of an obstacle. The intensity of light at a specific point on the screen behind the obstacle depends on the number of half-period zones contributing to the light reaching that point.Here's a breakdown of the concept:Huygens' principle: This principle states that every point on a wavefront acts as a secondary source of wavelets, and these wavelets spread out in all directions.Half-period zones: When light from a source encounters an obstacle, the edge acts as a new source of wavelets. These wavelets can interfere with each other, either constructively or destructively, depending on their relative phase shifts. We can divide the wavefront emerging from the obstacle into zones of equal areas, called half-period zones. The first zone closest to the edge contributes the most to the diffracted light, while subsequent zones contribute progressively less due to the accumulating phase difference.Intensity at a point: The intensity of light at a particular point on the screen is determined by the summation of the wavelets arriving from all the half-period zones at that point. If the wavelets arrive in phase, they reinforce each other, leading to a bright spot. Conversely, if they arrive out of phase, they cancel each other partially or completely, resulting in a dark spot.Therefore, the number of half-period zones superposing at a point directly influences the intensity of light observed at that point in the diffraction pattern