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A paralel beam of light incident on a co...

A paralel beam of light incident on a concave lens of focal length 10 cm emerges as a parallel beam from a convex lens placed coaxially, the distance between the lenses being 10 cm. The focal length of the convex lens in cm is

A

10

B

15

C

20

D

30

Text Solution

Verified by Experts

The correct Answer is:
C

Image by concave lens is formed at its focus i.e., at `I_1`, after refraction from concave lens, rays become parallel to principal axis i.e., they are coming from focus of convex lens.
`f_2=10+10=20cm`
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CP SINGH-REFRACTION AT SPHERICAL SURFACES-EXERCISES
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