A light wave can travel:

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

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. \(x+y+z=c\)

When the light diverges from a point source, the shape of the wavefront is:
1. Parabolic.
2. Plane.
3. Spherical.
4. Elliptical.

For light diverging from a point source:

Which of the following is not true?

When the light is coming from a distant star that is intercepted by the earth, the shape of the wavefront is:

The refractive index of glass is \(1.5\). What is the speed of light in glass? 
1. \(2 \times 10^{8}~\text{m/s}\)
2. \(3 \times 10^{8} ~\text{m/s}\)
3. \(1.5 \times 10^{8} ~\text{m/s}\)
4. \(2.2 \times 10^{8}~\text{m/s}\)

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