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

$PQ$ represents a wavefront and $AO$ and $BP$ are the corresponding two rays. Find the condition on $Q$ for constructive interference at $P$ between ray $BP$ and the reflected ray $OP$.

Two periodic waves of intensities $I_{1}$ and $I_{2}$ pass through a region at the same time in the same direction. The sum of the maximum and minimum intensities is

Two point sources $S_1$ and $S_2$ separated by a distance $10 \mu m$ emit light waves of wavelength $4 \mu m$ in phase. $A$ circular wire of radius $40 \mu m$ is placed around the sources as shown in the figure,where $O$ is the centre of the circle and $OS_1 = OS_2$. Then:

The intensity of light depends upon:

The resultant amplitude of coherent sources depends on ......