# 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

Subtopic:  Refraction at Plane Surface |
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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

Subtopic:  Reflection at Spherical Surface |
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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

Subtopic:  Reflection at Spherical Surface |
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The graph between u and v for a convex mirror is:

 1 2 3 4
Subtopic:  Reflection at Spherical Surface |
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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)                             (b)

(c)                             (d) It is not possible

Subtopic:  Prisms |
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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

Subtopic:  Lenses |
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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

Subtopic:  Refraction at Plane Surface |
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For a concave mirror, if the virtual image is formed, the graph between m and u is of the form :

Subtopic:  Reflection at Spherical Surface |
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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

Subtopic:  Lenses |
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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 $2×{10}^{8}m}{sec}$, the focal length of the lens is

1. 15 cm

2. 20 cm

3. 30 cm

4. 10 cm

Subtopic:  Lenses |
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