A thin prism having refracting angle $10°$ is made of glass of refractive index $1.42$ This prism is combined with another thin prism of glass of refractive index $1.7.$ This combination produces dispersion without deviation. The refracting angle of second prism should be

An object is placed at a distance of $40 \mathrm{cm}$ from a concave mirror of focal length $15 \mathrm{cm}$. If the object is displaced through a distance of $20 \mathrm{cm}$ towards the mirror, the displacement of the image will be:

Find the position of the final image from $O$ for the arrangement shown.

Find linear magnification in the given diagram.