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 the distance d between them. If a parallel beam of light falling on A leaves B as a parallel beam, then distance d in cm will be
A
25
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B
15
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C
30
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D
50
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Solution
The correct option is B 15 From figure it is clear that separation between lenses
d =20-5=15 cm