The radius of the curved surface of a plano-convex lens is $20 \, cm$ and the refractive index of the lens material is $1.5$. Calculate the equivalent focal length of the lens if the curved surface is silvered.

$A$ thin plano-convex lens acts like a concave mirror of focal length $0.2 \ m$ when silvered from its plane surface. The refractive index of the material of the lens is $1.5$. The radius of curvature of the convex surface of the lens will be.......$m$.

$A$ planoconvex lens,when silvered at its plane surface,is equivalent to a concave mirror of focal length $28 \ cm$. When its curved surface is silvered and the plane surface is not silvered,it is equivalent to a concave mirror of focal length $10 \ cm$. The refractive index of the material of the lens is:

One face of a rectangular glass plate $6 \, cm$ thick is silvered. An object held $8 \, cm$ in front of the first face forms an image $12 \, cm$ behind the silvered face. The refractive index of the glass is

Given is a thin convex lens of glass (refractive index $\mu$) and each side having radius of curvature $R$. One side is polished for complete reflection. At what distance from the lens,an object be placed on the optic axis so that the image gets formed on the object itself?

$A$ planoconvex lens becomes an optical system of $28 \, cm$ focal length when its plane surface is silvered and illuminated from left to right as shown in Fig $-A$. If the same lens is instead silvered on the curved surface and illuminated from the other side as in Fig. $-B$, it acts like an optical system of focal length $10 \, cm$. The refractive index of the material of the lens is