A plano convex lens has focal length `f = 20 cm`. If its plano surface is silvered, then new focal length will be.A. 20 cmB. 40 cmC. 30 cmD. 10 cm

A plano convex lens has focal length `f = 20 cm`. If its plano surface

1.	A plano convex lens has focal length `f = 20 cm`. If its plano surface is silvered, then new focal length will be.A. 20 cmB. 40 cmC. 30 cmD. 10 cm
Answer» Correct Answer - D (d) The focal length of the plano-convex lens is 20 cm with the plane surface bieng silvered. So, the net power of the lens is given by `P=1/fxx2=2/f` Thus, the net focal length is, `f/2=20/2=10 cm`

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A plano convex lens has focal length `f = 20 cm`. If its plano surface is silvered, then new focal length will be.A. 20 cmB. 40 cmC. 30 cmD. 10 cm

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