When light is refracted, which of the following does not change?
1. wavelength
2. frequency
3. velocity
4. amplitude

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. \(\mathrm{cos^{-1}\left(\frac{1}{\sqrt{3}}\right )}\)

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

A light wave can travel:

Choose the correct option:
1. (a) and (b)
2. (b) and (c)
3. (a) and (c)
4. (c) and (d)

Huygens' principle of secondary wavelets may be used to:

Choose the correct option:
1. (a) and (b)
2. (b) and (c)
3. (c) and (d)
4. All of these

Light waves travel in vacuum along the X-axis. Which of the following may represent the wavefronts?
1. \(x=c\)
2. \(y=c\)
3. \(z=c\)
4. \(x+y+z=c\)