Interference cannot be observed in two sodium lamps of equal power because the two waves do not have a .....

The ratio of the intensities of two waves is $25 : 1$. If interference occurs,then the ratio of the maximum and minimum intensity should be:

Two coherent sources produce waves of different intensities which interfere. After interference,the ratio of the maximum intensity to the minimum intensity is $16$. The ratio of the intensities of the waves is:

If $L$ is the coherence length and $c$ is the velocity of light,the coherence time is

If the wavelength of light is $4000 \mathring A$,then the number of waves in $1 \ mm$ length will be

In an interference pattern,two waves of intensities $I$ and $4I$ are used. At point $A$,the phase difference is $\frac{\pi}{2}$,and at point $B$,the phase difference is $\pi$. The difference in intensities at points $A$ and $B$ is: (in $I$)