To increase the magnifying power of a telescope:

1.	The focal length of the eyepiece should be increased.
2.	The focal length of the objective should be increased.
3.	The wavelength of light should be increased.
4.	The aperture of the eyepiece should be increased.

A ray of light is incident on a prism of angle A and refractive index $\mu$ will not emerge out of prism for any angle of incidence, if

(1) $\mu >\sin \frac{A}{2}$

(2) $\mu >\cos A$

(3) $\mu <\frac{1}{\sin A}$

(4) $\mu >\frac{1}{\sin {\displaystyle \frac{A}{2}}}$

What should be the maximum angle of acceptance at the air core interface of an optical fiber, if $n_1 and n_2$ are the refractive indices of the core and the cladding respectively?

(1) ${\sin }^{-1}\left(\frac{n_2}{n_1}\right)$

(2) ${\sin }^{-1}\sqrt{n_1^2-n_2^2}$

(3) ${\tan }^{-1}\left(\frac{n_2}{n_1}\right)$

(4) ${\sin }^{-1}\left(\frac{n_1}{n_2}\right)$

Two positions of the convex lens for which the image of the object is formed on the same screen are 40 cm and 80 cm from the object. The focal length of the lens is

1.  $\frac{80}{3}cm$

2.  $\frac{40}{3}cm$

3.  40 cm

4.  80 cm

A person cannot see objects clearly that are closer than 2 m and farther than 4 m. To correct the eye vision, the person will use:

(1) Bifocal lenses of power -3.5 D and 0.25 D

(2) Bifocal lenses of power -0.25D and 3.5 D

(3) Bifocal lenses of power -0.5D and 4.0D

(4) Bifocal lenses of power -4.0D and 0.5 D

A graph is plotted between the angle of deviation $\delta$ in a triangular prism and the angle of incidence as shown in the figure. Refracting angle of the prism is: 

 
1. \(28^\circ\)
2. \(48^\circ\)
3. \(36^\circ\)
4. \(46^\circ\)

Minimum distance between real object and image produced by a concave mirror of focal length 20 cm is:

(1) 80 cm

(2) zero

(3) 20 cm

(4) 40 cm

Three lenses A, B and C are shown in the figure. Lens A is concave lens. B and C are plano-convex lenses. All the lenses have same focal length f. In which case the spherical; aberration is minimum?

1.  A

2.  B

3.  C

4.  All of the above