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

1.	a large aperture contributes to the quality and visibility of the images.
2.	a large area of the objective ensures better light-gathering power.
3.	a large aperture provides a better resolution.
4.	all of the above.

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:

Find the value of the angle of emergence from the prism given below for the incidence ray shown. The refractive index of the glass is \(\sqrt{3}\).

1. \(45^{\circ}\)
2. \(90^{\circ}\)
3. \(60^{\circ}\)
4. \(30^{\circ}\)$\mathrm{}$

A magician during a show makes a glass lens with \(n=1.47\) disappear in a trough of liquid. What is the refractive index of the liquid? 
1. \( 1.47 \)
2. \( 1.33 \)
3. \(0.66 \)
4. \( 1.5\)

The image formed by a concave mirror:

To increase the angular magnification of a simple microscope, one should increase:

A rod of length \(10~\text{cm}\) lies along the principal axis of a concave mirror of focal length \(10~\text{cm}\) in such a way that its end closer to the pole is \(20~\text{cm}\) away from the mirror. The length of the image is:
1. \(15~\text{cm}\) 
2. \(2.5~\text{cm}\)
3. \(5~\text{cm}\)
4. \(10~\text{cm}\)

For the angle of minimum deviation of a prism to be equal to its refracting angle, the prism must be made of a material whose refractive index:

If the critical angle for total internal reflection from a medium to vacuum is \(45^{\circ}\), the velocity of light in the medium is: