Two symmetric double convex lenses A and B have same focal length but the radii of curvature differ so that `R_(A) = 0.9R_(B)`. If refractive index of A is 1.63 find the refractive index of B.

Options

A. `1.7`
B. `1.6`
C. `1.5`
D. `4//3`

Answer

C

Explanation

`(1)/(f)=(mu-1)((1)/(R_(1))-(1)/(R_(2))) (1)/(f)=(1.63-1)((2)/(R_(A)))=(n_(B)-1)((2)/(R_(B)))`
`n_(B)-1=0.63xx(R_(B))/(R_(1))=(0.63)/(0.9)=0.7 , n_(B)=1.7`