ray optics Questions

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 $20\text{cm}$ and a concave lens ‘B’ of focal length $5\text{cm}$ 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 cm will be:

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

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