Two light waves of intensities $I_0$ and $9I_0$ superpose at a point to produce a resultant intensity of $7I_0$. Calculate the phase difference between the light waves.

Two coherent monochromatic beams of intensities $I$ and $4I$ respectively are superposed. The maximum and minimum intensities in the resulting pattern are

Two light waves of intensities $I_1$ and $I_2$ having the same frequency pass through the same medium at a time in the same direction and interfere. The sum of the minimum and maximum intensities is

If the ratio of maximum and minimum intensities is $36 : 1$ in an interference pattern,then the ratio of amplitudes of the interfering waves is

Among the two interfering monochromatic sources $A$ and $B$; $A$ is ahead of $B$ in phase by $66^\circ$. If the observation is taken from point $P$,such that $PB - PA = \lambda / 4$. Then the phase difference between the waves from $A$ and $B$ reaching $P$ is.....$^\circ$.

Two coherent sources of light can be obtained by