The refractive index of the material ofa double convex lens is 1.5 and its focal length is 5 cm. If the radii of curvature are equal, the value of the radius of curvature (in cm) is

Options

A. 5
B. 6.5
C. 8
D. 9.5

Answer

A

Explanation

From Lens Makers formula,
For thin lens, `1/f =-(mu-1)(1/R_(1) – 1/R_(2))`
`implies 1/5 =(1.5-1) (2/R) (because R_(1)=R_(2)=R)`
`therefore R=5cm`