Question:

A thin lens has focal length fi and its aperture has diameter d. It forms an image of intensity I. Now the central part of the d/2 aperture upto diameter is blocked by an opaque paper. The focal length and image intensity will change to

Options :

  • (a) f/2 and I/2
  • (b) f and I/4
  • (c) 3f/4 and I/2
  • (d) f and 3I/4

Answer :

(d) f and 3I/4

Answer Steps :

step 1

step 2

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