A glass convex lens is of refractive index 1 55 with both faces of same radius of curvature. What will be the radius of curvature if focal length is to be 20 ~cm ?

Step-by-step solution

Lens maker's formula, ( 1 f =( -1) ( 1 R ₁ - 1 R ₂ ) ) Here, ( f =20 ~cm , =1.55, R ₁= R , R ₂=- R ) ( aligned & 1 20 =(1.55-1) ( 1 R - 1 (-R) ) or 1 20 =0.55 2 R & R=1.1 20=22 ~cm aligned )