If the behavior of light rays through a convex lens is as shown in the adjoining figure,then

$A$ candle placed $25 \ cm$ from a lens forms an image on a screen placed $75 \ cm$ on the other side of the lens. The focal length and type of the lens should be

$A$ lens of refractive index $n$ is placed in a liquid of refractive index $n'$. If the focal length of the lens in air is $f$,what will be its focal length in the liquid?

$A$ diminished image of an object is to be obtained on a large screen $1\, m$ from it. This can be achieved by

$A$ convex lens of focal length $f$ is placed somewhere in between an object and a screen. The distance between the object and the screen is $x$. If the numerical value of the magnification produced by the lens is $m$, then the focal length of the lens is

$A$ 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.......$cm$.