Which of the following sources gives the best monochromatic light?
1. a candle
2. a bulb
3. a mercury tube
4. a laser

Two sources are called coherent if they produce waves:

Two coherent sources of different intensities send waves which interfere. The ratio of maximum intensity to the minimum intensity is \(25.\) The intensities of the sources are in the ratio:
1. \(25:1\)
2. \(5:1\)
3. \(9:4\)
4. \(625:1\)

The slits in a Young's double-slit experiment have equal width and the source is placed symmetrically with respect to the slits. The intensity at the central fringe is \(I_0.\) If one of the slits is closed, the intensity at this point will be:
1. \(I_0\)
2. \(I_0/4\)
3. \(I_0/2\)
4. \(4I_0\)

A thin transparent sheet is placed in front of a Young's double-slit. The fringe-width will:
1. increase
2. decrease
3. remain same
4. become nonuniform

If Young's double-slit experiment is performed in water,

1. the fringe width will decrease

2. the fringe width will increase

3. the fringe width will remain unchanged

4. there will be no fringe

If the source of light used in a Young's double-slit experiment is changed from red to violet,

A Young's double slit experiment is performed with white light.

(a) The central fringe will be white

(b) There will not be a completely dark fringe

(c) The fringe next to the central will be red

(d) The fringe next to the central will be violet

Choose the correct option:

1. (a) and (b)

2. (b) and (c)

3. (a), (b) and (d)

4. (a), (b) and (c)

Four light waves are represented by
(i)    y = a1 sin ωt        (ii)    y = a2 sin (ωt + ε)
(iii)    y = a1 sin 2ωt    (iv)    y = a2 sin 2(ωt + ε)

Interference fringes may be observed due to superposition of

(a) (i) and (ii)

(b) (i) and (iii)

(c) (ii) and (iv)

(d) (iii) and (iv)

Choose the correct option:

1. (a) and (b)

2. (b) and (c)

3. (c) and (d)

4. (a) and (d)