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

(1) 25                         

(2) 15

(3) 30                         

(4) 50

A medium shows relation between i and r as shown. If the speed of light in the medium is nc then the value of n is:

1. 1.5

2. 2

3. 2^–1

4. 3^–1/2

For a concave mirror, if the virtual image is formed, the graph between m and u is of the form :

A luminous object is placed at a distance of 30 cm from the convex lens of focal length 20 cm. On the other side of the lens, at what distance from the lens, a convex mirror of radius of curvature 10 cm be placed in order to have an upright image of the object coincident with it?

(1) 12 cm                             

(2) 30 cm

(3) 50 cm                             

(4) 60 cm

Which one of the following spherical lenses does not exhibit dispersion? The radii of curvature of the surfaces of the lenses are as given in the diagrams

The size of the image of an object, which is at infinity, as formed by a convex lens of focal length 30 cm is 2 cm. If a concave lens of focal length 20 cm is placed between the convex lens and the image is at a distance of 26 cm from the convex lens, calculate the new size of the image.

(1) 1.25 cm                             

(2) 2.5 cm

(3) 1.05 cm                             

(4) 2 cm

An achromatic prism is made by crown glass prism $\left(A_c=19°\right)$ and flint glass prism $\left(A_F=6°\right)$. If ${}_C\mu _v=1.5$ and ${}_F\mu _v=1.66$, then resultant deviation for red coloured ray will be

(a) 1.04°                     (b) 5°

(c) 0.96°                      (d) 13.5°

An isosceles prism of angle 120° has a refractive index of 1.44. Two parallel monochromatic rays enter the prism parallel to each other in air as shown. The rays emerging from the opposite faces :

(a) Are parallel to each other

(b) Are diverging

(c) Make an angle $2{\sin }^{-1}\left(0.72\right)$ with each other

(d) Make an angle $2\left\{{\sin }^{-1}\left(0.72\right)-30°\right\}$ with each other

A ray of light is incident on the hypotenuse of a right-angled prism after travelling parallel to the base inside the prism. If $\mu$ is the refractive index of the material of the prism, the maximum value of the base angle for which light is totally reflected from the hypotenuse is 

(a) ${\sin }^{-1}\left(\frac{1}{\mu }\right)$                             (b) ${\tan }^{-1}\left(\frac{1}{\mu }\right)$

(c) ${\sin }^{-1}\left(\frac{\mu -1}{\mu }\right)$                         (d) ${\cos }^{-1}\left(\frac{1}{\mu }\right)$