Find the refractive index of the material of a plano-convex lens, if the radius of curvature of the convex surface is 20 cm and focal length of the lens is 60 cm?

Explanation

Given, `R_(1)=oo,R_(2)=20 cm,f=60cm,mu=?`
From Lens Maker's formula, we have
`1/f=(mu-1)(1/R_(1)-1/R_(2))`
`rArr1/60=(mu-1)(1/(oo)-1/(-20))=(mu-1)/20`
`therefore` Refractive index,`mu=1+1/3=4/3`