Question

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 :

• A. the focal length of lens used for observation
• B. the number of half-period zones that superpose at the point
• C. the square of the sum of the number of half period zones
• D. the thickness of the obstacle

Answer 1

The correct option is B the number of half-period zones that superpose at the point

In Fresnel diffraction, the intensity reduces from the central peak as we move towards edges. Hence, the intensity of light at a point on screen beyond obstacle will depend on the number of half-period zones that superpose at the point.