[" To observe a stationary "],[" interference pattern formed by "],[" two light waves,it is not "],[" necessary that they must have "]

To observe a stationary interference pattern formed by two light waves, which of the following is not a necessary condition:

To obtain steady or sustained interference pattern, two sources of light should be

What will happen to interference pattern if two sources of light are not in same phase ?

For steady interference, two two sources of light must be

For steady interference of light, the two sources of light must be

For sustained and sharp interference pattern, the wave length of the interference waves should :

What change is observed in interference pattern of Young's double slit experiment ,if one of the two slits is painted,so that it transmits half the light intensity of the other?

State the necessary conditions for the interference of two sound waves.