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

Answer

`1.75`

Explanation

Here, `f = (2)/(3)R`, where `R_(1) = R, R_(2) = - R, mu = ?`
From `(1)/(f) = (mu - 1)((1)/(R_(1)) - (1)/(R_(2)))`
`(3)/( 2R) = (mu - 1)/((1)/(R ) + (1)/(R )) = (mu - 1)(2)/(R )`
`mu - 1 = (3)/(4) = 0.75, mu = 1.75`