A concave mirror of radius of curvature $R=40 \mathrm{cm}$ is placed inside water $\left(\mu =\frac{4}{3}\right)$ of depth $30 \mathrm{cm}.$ A parallel beam of light is incident on water surface as shown. The distance of final image is

A point object is placed in the arrangement shown. The distance of image formed by lens-$2$ from its optical centre is

An equiconvex lens $(\mu =1.5)$ of focal length $f=20 \mathrm{cm}$ is placed on a plane mirror. A liquid of $\mu =\frac{4}{3}$ is filled between the gap as shown. At what distance from the lens an object should be placed so that a virtual image of double the size of object is formed?

A thin lens is made in the shape of a disc of thickness $d$ and radius $R.$ The refractive index $\left(\mu \right)$ of material of disc varies with distance $r$ from the centre. If parallel beam of light get focused at distance $f>>R$ from the lens, then (refractive index at centre of disc is ${\mu }_0$)

Figure shows an object $O$ kept at $P.$ A plane mirror parallel to $yz$ plane is moving with velocity $3\hat{i} \mathrm{m} {\mathrm{s}}^{-1}.$
Select the correct alternative