Two coherent sources must have .......

Two light waves of intensities $I$ and $2I$ superimpose on each other. If the path difference between the light waves reaching a point is $12.5 \%$ of the wavelength of the light,then the resultant intensity at the point is (Both the light waves have same wavelength).

If the ratio of amplitudes of two interfering waves is $4: 3$,then the ratio of maximum and minimum intensity is

Two light beams of intensities $I$ and $4I$ produce an interference pattern on a screen. If the phase difference between them at point $A$ is $\pi/2$ and at point $B$ is $2\pi$,find the difference between the resultant intensities at points $A$ and $B$.

Two sources of waves are called coherent if

Diffraction and interference of light suggest