A biconvex lens has focal length `(2)/(3)` times the radius of curvature of either surface. Calculate refractive index of material of the lens.

Options

A. `1.75`
B. `1.33`
C. `1.5`
D. `1.0`

Answer

A

Explanation

Using lens maker's formula,
`1/f = (mu-1) ((1)/(R_(1)) - (1)/(R_(2)))`. Here,`f = 2/3R, R_(1) = +R, R_(2) = -R`
`:. (1)/((2//3)R) = (mu-1)((1)/(R) + (1)/(R)) = ((mu-1)xx2)/(R) rArr mu = 1.75`