Question

Find the focal length of plano convex lens whose radius of curvature is 20cm and refractive index of glass is 1.5

Answer 1

1/f=(n-1)*(1/R1-1/R2) where n is refractive index which is given 1.5 and R1 and R2 are two radius of curvature of two surface of the plano convex lens.

1/f=(n-1)*(1/R-1/infinity)

or, 1/f=(1.5-1)*1/20

or, 1/f=0.5*1/20

or, f=40

Answer 2

Answer:

40

Explanation:

focal length is equal to twice the radius of curvature i.e, f = 2R