NEET UG 2021 — Optics

A point object is placed at a distance of $60\mathrm{cm}$ from a convex lens of focal length $30\mathrm{cm}$. If a plane mirror were put perpendicular to the principal axis of the lens and at a distance of $40\mathrm{cm}$ from it, the final image would be formed at a distance of : 

Find the value of the angle of emergence from the prism. Refractive index of the glass is $\sqrt{3}$. 

A lens of large focal length and large aperture is best suited as an objective of an astronomical telescope since:

A convex lens $A$ of focal length $20\mathrm{cm}$ and a concave lens $B$ of focal length $5\mathrm{cm}$ are kept along the same axis with a distance $d$ between them. If a parallel beam of light falling on $A$ leaves $B$ as a parallel beam, then the distance $d$ in $\mathrm{cm}$ will be :