A plano convex lens (f = 20 cm) is silvered at plane surface. Now f will be

Q. A plano-convex lens $(f=20cm)$ is silvered at plane surface. Now focal length will be :

Q. A plano-convex lens (f=20 cm) is silvered at plane surface. The focal length will be

Q. A plano-convex lens of f=20 cm is silvered at plane surface, now , its focal length is $(\mu =1.5)$

Q. The plane surface of a plano-convex lens of focal length f is silvered. It will behave as:

Q. A plano-convex lens of focal length $20$ cm silvered at the plane surface will behave as a convergent mirror of focal length ______ $cm$.