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The focal length of the lens of refracti...

The focal length of the lens of refractive index `(mu = 1.5)` in air is 10 cm. If air is replaced by water of `mu = (4)/(3)`, its focal length is

A

20 cm

B

30 cm

C

40 cm

D

25 cm

Text Solution

Verified by Experts

The correct Answer is:
C
`(f_(w))/(f_(a)) = (mu - 1)/((mu_(w))/(mu_(a)) - 1)`
`(f_(w))/(10) = (1-5-1)/(1//8)`
`f_(w) = (0.5 xx 10)/(1//8) = 40` cm
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