# A thin lens has focal length f, and its aperture has diameter d. It forms an image of intensity I. Now, the central part of the aperture up to diameter d/2 is blocked by an opaque paper The image intensity will change toChoose the correct answer:a. f/2 and I/2b. f and I/4c. 3f /4 and I/2d. f and 3I/4

Arun
25757 Points
4 years ago

Focal length will remains same.

Intensity is directly proportional to the area of the aperture of the lens receiving  the light.

Total area of the aperture is,

A = pi * d²/4

Remaining area after covering,

A' = pi *(d²/4  - d²/16) = 3 * pi* d²/16

I/I' = A/A' = 4/3

I' = 3 I/4

Regards

Rishi Sharma
2 years ago
Dear Student,