When light is refracted, which of the following does not change?
1. wavelength
2. frequency
3. velocity
4. amplitude
The amplitude modulated (AM) radio wave bends appreciably round the corners of a 1m × 1m board but the frequency modulated (FM) wave only negligibly bends. If the average wavelengths of AM and FM waves are \(\lambda_a\) and \(\lambda_f\),
1. \(\lambda_a\) > \(\lambda_f\)
2. \(\lambda_a\) = \(\lambda_f\)
3. \(\lambda_a\) < \(\lambda_f\)
4. we don't have sufficient information to decide about the relation of \(\lambda_a\) and \(\lambda_f\)
Which of the following sources gives the best monochromatic light?
1. a candle
2. a bulb
3. a mercury tube
4. a laser
The wavefronts of a light wave travelling in vacuum are given by \(x+y+z=c\). The angle made by the direction of propagation of light with the X-axis is:
1. \(0^{\circ}\)
2. \(45^{\circ}\)
3. \(90^{\circ}\)
4. \({\cos^{-1}\left({1}/{\sqrt{3}}\right )}\)
The wavefronts of light coming from a distant source of unknown shape are nearly:
1. plane
2. elliptical
3. cylindrical
4. spherical
The inverse square law of intensity (i.e., the intensity \(\propto \frac{1}{r^2})\) is valid for:
1. a point source
2. a line source
3. a plane source
4. a cylindrical source
Two sources are called coherent if they produce waves:
1. | of equal wavelength |
2. | of equal velocity |
3. | having same shape of wavefront |
4. | having a constant phase difference |
When a drop of oil is spread on a water surface, it displays beautiful colours in daylight because of:
1. | dispersion of light | 2. | reflection of light |
3. | polarization of light | 4. | interference of light |
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. \(4I_0\)