. A plano-covex lens is silvered on its plane-side and then it acts like a concave mirror of focal length 20 cm. When the convex side is silvered it acts like a concave mirror of 7 cm focal length. Wh

Question

. A plano-covex lens is silvered on its plane-side and then it acts like a concave mirror of focal length 20 cm. When the convex side is silvered it acts like a concave mirror of 7 cm focal length. What is the radius of curvature curved surface of the lens?

TestHub · Accepted Answer

F 1 ​ = − ( μ − 1 ) R 1 ​ ⇒ − 20 1 ​ = − 2 ( μ − 1 ) R 1 ​ F 2 ​ 1 ​ = − 2 ( μ − 1 ) R 1 ​ + − R 2 ​ ⇒ − 7 1 ​ = − 2 ( μ − 1 ) R 1 ​ − R 2 ​ 7 1 ​ − 20 1 ​ = R 2 ​ = 140 13 ​ R = 13 280 ​ cm ​

Physics - Geometrical Optics Question with Solution | TestHub

Options:

Doubts & Discussion