The phenomenon of interference is exhibited by:

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

Four monochromatic and coherent sources of light,emitting waves in phase of wavelength $\lambda$,are placed at the points $x = 0, d, 2d$,and $3d$ on the $x$-axis. The intensity of the waves reaching a point $P$ far away on the $+x$ axis from each of the four sources is almost the same,and equal to $I_0$. Then,

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

Two coherent sources have different intensities. They produce an interference pattern. If the ratio of maximum to minimum intensities is $25:1$,find the ratio of the intensities of the sources.

When two light waves of equal intensity superimpose, the maximum intensity obtained is $I$. If the intensity of one of the waves is quadrupled, then the maximum intensity obtained is