If $\frac{\text{Path difference}}{\text{Wave length}} = n$ (where $n$ is an integer),what kind of interference is formed?

$A$ ray of light from a monochromatic point source of light is incident at a point on the screen. If a thin mica film of thickness $t$ and refractive index $n$ is introduced in its path,then the optical path

Two light waves of intensities $I$ and $4I$ superpose at a point with a phase difference of $\pi / 2$. Calculate the resultant amplitude at that point.

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

Two point sources separated by $d = 5\, \mu m$ emit light of wavelength $\lambda = 2\, \mu m$ in phase. $A$ circular wire of radius $R = 20\, \mu m$ is placed around the sources as shown in the figure. Determine the nature of interference at points $A, B, C,$ and $D$.

To demonstrate the phenomenon of interference,we require two sources which emit radiation: