A double convex lens of f = 6 cm is made of glass of refractive index 1.5. The radius of curvature of the surface which is double that of other surface will be

Options

A. 1.5 cm
B. 2.5 cm
C. 3.5 cm
D. 4.5 cm

Answer

D

Explanation

From Lens maker formula,
`1/f=(mu-1)(1/R_(1) – 1/R_(2))`
`implies 1/f=(mu-1)(1/R – 1/(2R))( because R_91)=R_(1)R_(2)=2R)`
`therefore 1/f=(mu-1)(3/(2R))`
`R=0.5xx6xx3/2=4.5cm`