In an interference experiment,the phase difference for points where the intensity is minimum is $(n=1, 2, 3, \ldots)$

Two coherent sources of intensity ratio $1 : 4$ produce an interference pattern. The fringe visibility will be

In an interference experiment,the path difference between two interfering waves at a point $A$ on the screen is $\lambda/3$,where $\lambda$ is the wavelength of these waves,and at another point $B$ the path difference is $\lambda/6$. The ratio of intensities at points $A$ and $B$ is . . . . . . .

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: The phase difference of two light waves changes if they travel through different media having the same thickness,but different indices of refraction.
Reason $R$: The wavelengths of waves are different in different media.
In the light of the above statements,choose the most appropriate answer from the options given below.

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,

Write the condition of destructive interference in terms of path and phase difference.