The radius of curvature of the faces of a double convex lens are `10 cm and 15 cm`. If focal length of lens of lens is `12 cm`, find the refractive index of the material of the lens.

Explanation

Hence, `R_1=10 cm, R_2= -15 cm , f = 12 cm , mu = ? `
Using lens formula, we have
` (1)/( f) =(mu-1) ((1)/(R_1)-(1)/(R_2))rArr (1)/(12) =(mu-1)((1)/(10)-(1)/(15))`
` rArr (1)/(12) = (mu-1) ((1)/(10)+(10)/(15))`
` rArr (1)/(12)=(mu-1)((3+2)/(3))rArr (1)/(12)=(mu-1)((5)/(3))`
`rArr (mu-1)=(1)/(12)xx(30)/(5)rArr mu-1=0.5rArr mu=1+0.5therefore mu=1.5`.