A convex lens A of focal length 20 cm an...

A convex lens A of focal length `20 cm` and a concave lens B of focal length `5 cm` are kept along the same axis with a distance d between them. If a parallel beam of light falling on A and B as a parallel beam, then d is equal to ……cm

25 cm

zero

15 cm convex and plane

10 cm

Text Solution

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The correct Answer is:

Image by convex lens is formed at distance 20 cm from it i.e, at `I_1`. The final rays are parallel to principal axis i.e., `I_1` is at focus of concave lens.
`20-d=5impliesd=15cm`

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