Question
Question: A biconvex lens of focal length f forms a circular image of radius r in focal plane. Then –...
A biconvex lens of focal length f forms a circular image of radius r in focal plane. Then –
A
pr2µ f2
B
pr2µ f
C
If lower half is covered by black sheet, then area of the image is equal to
D
If f is doubled, intensity will increase
Answer
pr2µ f2
Explanation
Solution

fr=tana \ r = f tan a
Area = pr2 = pf2 (tan a)2
\ pr2 µ f2