Optics 6 Question 17

19. A biconvex lens of focal length f forms a circular image of radius r of sun in focal plane. Then which option is correct?

(a) πr2f

(2006,3M)

(b) πr2f2

(c) If lower half part is convered by black sheet, then area of the image is equal to πr2/2

(d) If f is doubled, intensity will increase

Show Answer

Solution:

 or rf

πr2f2



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