Two coherent sources of light interfere and produce a fringe pattern on a screen. For the central maximum,the phase difference between the two waves will be,

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

Two coherent sources of intensities $I_{1}$ and $I_{2}$ produce an interference pattern on a screen. The maximum intensity in the interference pattern is

If the ratio of the intensities of two waves producing interference is $49: 16$,then the ratio of the resultant maximum intensity to minimum intensity will be

Two coherent waves of equal intensity produce a maximum intensity of $100$ units. If the intensity of one of the sources is reduced by $20\%$,then the new maximum intensity will be:

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 $OS_1 = OS_2$. Determine the nature of the interference at points $A, B, C,$ and $D$.