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Focal length of thin lens of refractive ...

Focal length of thin lens of refractive index 1.5 is 15 cm. When placed on liquid of refractive index `4/3`, then its focal length will be ...... cm.

A

80.31

B

50

C

78.23

D

60

Text Solution

Verified by Experts

The correct Answer is:
D
`1/(15) = (1.5-1) (1/(R_1) - 1/(R_2))`
`1/f = ((1.5)/(4//3)-1) (1/(R_1)- 1/(R_2))`
`f/(15) = (1//2)/((1//8))`
`f= 4 xx 15 = 60 `cm
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