## A rectangular glass slab ABCD of refractive index n1 is immersed in water of refractive index n2 (n1 > n2).

Q: A rectangular glass slab ABCD of refractive index n1 is immersed in water of refractive index n2 (n1 > n2). A ray of light is incident at the surface AB of the slab as shown. The maximum value of the angle of incidence αmax, such that the ray comes out only from the other surface CD, is given by (A) $\large sin^{-1}[\frac{n_1}{n_2}cos(sin^{-1}\frac{n_2}{n_1})]$

(B) $\large sin^{-1}[ n_1 cos(sin^{-1}\frac{1}{n_2})]$

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

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

Ans: (A)

## A point source of light S, placed at a distance L in front of the centre of a plane mirror of width d, hangs vertically on a wall…

Q: A point source of light S, placed at a distance L in front of the centre of a plane mirror of width d, hangs vertically on a wall. A man walks in front of the mirror along a line parallel to the mirror at a distance 2L from it as shown. The greatest distance over which he can see the image of the light source in the mirror is (A) d/2

(B) d

(C) 2 d

(D) 3 d

Ans: (D)

## In a double slit experiment instead of taking slits of equal widths, one slit is made twice as wide as the other…

Q: In a double slit experiment instead of taking slits of equal widths, one slit is made twice as wide as the other, then in the interference pattern

(A) the intensities of both the maxima and the minima increases

(B) the intensity of maxima increases and the minima has zero intensity

(C) the intensity of maxima decreases and that of minima increases

(D) the intensity of maxima decreases and the minima has zero intensity

Ans: (A)

## A diverging beam of light from a point source S having divergence angle α  falls symmetrically on a glass slab as equal…

Q: A diverging beam of light from a point source S having divergence angle α  falls symmetrically on a glass slab as equal. The angles of incidence of the two extreme rays are equal. If the thickness of the glass slab is t and its refractive index is n, then the divergence angle of the emergent beam is (A) zero

(B) α

(C) sin–1 (1/n)

(D) 2 sin–1 (1/n)

Ans: (B)

## A hollow double concave lens is made of very thin transparent material. It can be filled with air or either of two liquids…

Q: A hollow double concave lens is made of very thin transparent material. It can be filled with air or either of two liquids L1 or L2 having refracting indices n1 and n2 respectively (n2 > n1 > 1). The lens will diverge a parallel beam of light if it is filled with

(A) air and placed in air

(B) air and immersed in L1

(C) L1 and immersed in L2

(D) L2 and immersed in L1

Ans: (D)