The distance between a convex lens and a plane mirror is 10 cm. The parallel rays incident on the convex lens after reflection from the mirror form image at the optical centre of the lens. Focal length of the lens will be

(a)   10 cm

(b)   20 cm

(c)   30 cm

(d)   Cannot be determined

Concept Questions :-

Lenses
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Difficulty Level:

If the focal length of the objective lens and the eye lens is 4 mm and 25 mm respectively in a compound microscope. The length of the tube is 16 cm. Find its magnifying power for relaxed eye position

(a)   32.75                                 (b)  327.5

(c)   0.3275                               (d)  None of the above

Concept Questions :-

Simple and compound microscope
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Difficulty Level:

An air bubble in a sphere having 4 cm diameter that appears 1 cm from the surface nearest to the eye when looked along diameter. If${}_{a}\mu _{g}$ = 1.5, the distance of bubble from the refracting surface is

(a) 1.2 cm                    (b) 3.2 cm

(c) 2.8 cm                    (d) 1.6 cm

Concept Questions :-

Lenses
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Difficulty Level:

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

(a) $5/2$                                    (b) $\sqrt{\left(5/2\right)}$

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

Concept Questions :-

Refraction at plane surface
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Difficulty Level:

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

Concept Questions :-

Reflection at spherical surface
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Difficulty Level:

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 changes from 0 to  the graph between v versus u will be

Concept Questions :-

Reflection at spherical surface
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Difficulty Level:

The graph between u and v for a convex mirror is

Concept Questions :-

Reflection at spherical surface
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Difficulty Level:

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

Concept Questions :-

Total internal reflection
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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

(a) 25                         (b) 15

(c) 30                          (d) 50

Concept Questions :-

Lenses
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Difficulty Level:

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

(a)   1.5

(b)   2

(c)   2–1

(d)   3–1/2

Concept Questions :-

Refraction at plane surface