ADDITIONAL EXERCISES . The Å H ( line emitted by hydrogen in a star is found to be red- shifted by Å. Estimate the speed with which the star is receding from the Earth. .
Explain how Corpuscular theory predicts the speed of light in a medium, say, water, to be greater than the speed of light in vacuum. Is the prediction confirmed by experimental determination of the speed of light in water? If not, which alternative picture of light is consistent with experiment? .
You have learnt in the text how Huygens’ principle leads to the laws of reflection and refraction. Use the same principle to deduce directly that a point object placed in front of a plane mirror produces a virtual image whose distance from the mirror is equal to the object distance from the mirror. . Let us list some of the factors, which could possibly influence the speed of wave propagation: (i) nature of the source.
(ii) direction of propagation. (iii) motion of the source and/or observer. (iv) wavelength. (v) intensity of the wave.
On which of these factors, if any, does (a) the speed of light in vacuum, (b) the speed of light in a medium (say, glass or water), depend? . For sound waves, the Doppler formula for frequency shift differs slightly between the two situations: (i) source at rest; observer moving, and (ii) source moving; observer at rest. The exact Doppler formulas for the case of light waves in vacuum are, however, strictly identical for these situations.
Explain why this should be so. Would you expect the formulas to be strictly identical for the two situations in case of light travelling in a medium? . In double-slit experiment using light of wavelength nm, the angular width of a fringe formed on a distant screen is .1º.
What is the spacing between the two slits? . Answer the following questions: (a) In a single slit diffraction experiment, the width of the slit is made double the original width. How does this affect the size and intensity of the central diffraction band?
(b) In what way is diffraction from each slit related to the interference pattern in a double-slit experiment? (c) When a tiny circular obstacle is placed in the path of light from a distant source, a bright spot is seen at the centre of the shadow of the obstacle. Explain why? (d) Two students are separated by a m partition wall in a room m high.
If both light and sound waves can bend around