Question

Two plano convex lenses of same material and of focal lengths 20 cm & 5 cm should be arranged such that the combination is free from chromatic aberration. Then effective focal length of the combination will be:

A

20 cm

B

4 cm

C

12.5 cm

D

8 cm

Medium
Updated on : 2022-09-05
Solution
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Correct option is C)

The effective focal length of the lens is, 


Substituting the respective values, the effective focal length obtained is,

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