An object is placed at a distance $m$ times the focal length of a divergent lens. The size of the image is shorter than that of the object by what factor?

$A$ biconvex lens with equal radii of curvature has a refractive index of $1.6$ and a focal length of $10 \ cm$. Its radius of curvature will be.......$cm$.

When light rays from the sun fall on a convex lens along a direction parallel to its axis,which of the following statements is true?

The magnification of an object placed in front of a convex lens of focal length $20 \, cm$ is $+2$. To obtain a magnification of $-2$,the object has to be moved a distance equal to.....$cm$

$A$ point object in air is in front of the curved surface of a plano-convex lens. The radius of curvature of the curved surface is $30 \; cm$ and the refractive index of the lens material is $1.5$. Then the focal length of the lens (in $cm$) is:

$A$ convex lens of focal length $f$ produces a real image whose size is $n$ times the size of an object. The distance of the object from the lens is