A mark on the surface of sphere (µ = 3/2) is viewed from a diametrically opposite position. It appears to be at a distance \(15~\mathrm{cm}\) from its actual position. The radius of sphere is:
1. 15 cm
2. 5 cm
3. 7.5 cm
4. 2.5 cm

A light ray from the air is incident (as shown in the figure) at one end of glass fibre (refractive index µ = 1.5) making an incidence angle of 60° on the lateral surface so that it undergoes a total internal reflection. How much time would it take to traverse the straight fibre of a length of 1 km?
   
1. 3.33 $\mu s$

2. 6.67 $\mu s$

3. 5.77 $\mu s$

4. 3.85 $\mu s$

Choose the correct mirror image of the figure:
    

1.		2.
3.		4.

If there had been one eye of a man, then:

The near point of a person is 50 cm and the far point is 1.5 m. The spectacles required for reading purposes and for seeing distant objects are respectively:

1. + 2D, \(-\frac{2}{3}~D\)
2. \(+\frac{2}{3}~D\), - 2 D

3. - 2 D, \(+\frac{2}{3}~D\)

4. \(-\frac{2}{3}~D\), + 2 D

An astronomical refracting telescope will have large angular magnification and high angular resolution when it has an objective lens of:

An air bubble in a glass slab with refractive index 1.5 (near-normal incidence) is 5 cm deep when viewed from one surface and 3 cm deep when viewed from the opposite face. The thickness (in cm) of the slab is:

If the focal length of the objective lens is increased, then magnifying power of:

A ray of light is incident at an angle of incidence, i, on one face of a prism of angle A (assumed to be small) and emerges normally from the opposite face. If the refractive index of the prism is $\mu$, the angle of incidence i is nearly equal to:

A concave mirror of the focal length $f_1$ is placed at a distance of d from a convex lens of focal length $f_2$. A beam of light coming from infinity and falling on this convex lens-concave mirror combination returns to infinity. The distance d must be equal to:

1. $f_1+f_2$

2. $-f_1+f_2$

3. $2f_1+f_2$

4. $-2f_1+f_2$