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If in a plane convex lens the radius of curvature of the convex surface is 10 cm and the focal length of the lens is 30 cm, the refractive index of the material of the lens will be A. 1.5 B. 1.66 C. 1.33 D. 3

If in a plane convex lens the radius of curvature of the convex surface is 10 cm and the focal length of the lens is 30 cm, the refractive index of the material of the lens will be
A. 1.5 B. 1.66 C. 1.33 D. 3

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2 Answers

Saurabh Koranglekar
askIITians Faculty 10336 Points
2 years ago
Dear student

The answer is option c

Regards
Vikas TU
14149 Points
2 years ago
Let R1 AND R2   are the radius of curvature of the convex surface and plane surface of the planoconvex lens.
As per the question 
 R1 = 10 cm , R2 = infinite 
The focal length of the lens [f] = 30 cm.
From Lens maker's formula we know that-
1/30 = (mew -1 ) {1/10 - 1/ inf)                                   
                                              
Hence, the refractive index of the planoconvex lens is 4/3

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