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A thin convex lens of focal length 10 cm...

A thin convex lens of focal length 10 cm is placed in contact with a concave lens of same material and of same focal length. The focal length of combination will be

A

Zero

B

Infinity

C

10 cm

D

20cm

Text Solution

Verified by Experts

The correct Answer is:
B
According to the relation
`1/f = 1/(f_1) + 1/(f_2)`
`f = (f_1 f_2)/(f_1 + f_2) = (10 xx (-10))/(10 + (-10)) = (-100)/(0) = oo`
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