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Radius of curvature of plano-convex lens...

Radius of curvature of plano-convex lens is 10 cm. If its focal length is 30 cm, then its refractive index will be .......

A

1.1

B

1.22

C

1.33

D

1.66

Text Solution

Verified by Experts

The correct Answer is:
A, C
`R_1=infty` f=30 cm `R_2=-10` cm
`1/f=(n-1)(1/R_1-1/R_2)`
`(1)/(30)=(n-1)[(1)/(infty)-(1)/(-10)] implies (1)/(30)=(n-1)((1)/(10)) implies`
`1/3=n-1 thereforen=4/3=1.33`
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