An observer can see through a pinhole the top end of a thin rod of height h, placed as shown in the figure. The beaker height is 3h and its radius h. When the beaker is filled with a liquid up to a height 2h, he can see the lower end of the rod. Then the refractive index of the liquid is

                        

(1) $5/2$                                   

(2) $\sqrt{\left(5/2\right)}$

(3) $\sqrt{\left(3/2\right)}$                               

(4) 3/2

In an experiment of find the focal length of a concave mirror a graph is drawn between the magnitudes of u and v.  The graph looks like 

As the position of an object (u) reflected from a concave mirror is varied, the position of the image (v) also varies. By letting the u change from 0 to infinity, the graph between v versus u will be-

1.		2.
3.		4.

The graph between u and v for a convex mirror is:

1.		2.
3.		4.

A glass prism $\left(\mu =1.5\right)$ is dipped in water $\left(\mu =4/3\right)$ as shown in figure. A light ray is incident normally on the surface AB. It reaches the surface BC after totally reflected, if

(a) $\sin \theta \ge \raisebox{1ex}{$ 8$}\!\left/ \!\raisebox{-1ex}{$9$}\right.$                            (b) $\raisebox{1ex}{$2$}\!\left/ \!\raisebox{-1ex}{$3$}\right.<\sin \theta <\raisebox{1ex}{$ 8$}\!\left/ \!\raisebox{-1ex}{$9$}\right.$

(c) $\sin \theta \le \raisebox{1ex}{$2$}\!\left/ \!\raisebox{-1ex}{$3$}\right.$                            (d) It is not possible

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 speed of light in the medium is nc then 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 :

For a convex lens, the distance of the object is taken on X-axis and the distance of the image is taken on Y-axis, the nature of the graph so obtained is :

(1) Straight line                     

(2) Circle

(3) Parabola                          

(4) Hyperbola

The diameter of a plano-convex lens is 6 cm and thickness at the centre is 3 mm. If the

speed of light in the material of the lens is $2\times {10}^8\raisebox{1ex}{$m$}\!\left/ \!\raisebox{-1ex}{$sec$}\right.$, the focal length of the lens is

1. 15 cm                         

2. 20 cm

3. 30 cm                         

4. 10 cm