The phenomenon of interference is exhibited by:

$A$ and $B$ are two interfering sources where $A$ is ahead in phase by $54^{\circ}$ relative to $B$. The observation is taken from point $P$ such that $PB-PA=2.5 \lambda$. Then the phase difference between the waves from $A$ and $B$ reaching point $P$ is (in rad) (in $\pi$)

Two periodic waves of intensities $I_{1}$ and $I_{2}$ pass through a region at the same time in the same direction. The sum of the maximum and minimum intensities is

For a distinct interference pattern,the condition is that the ratio of intensities of light produced by both sources must be .....

Two waves having intensity $I$ and $9I$ produce interference. If the resultant intensity at a point is $7I$,what is the phase difference between the two waves?........$^o$

The difference in the number of wavelengths, when yellow light propagates through air and vacuum columns of the same thickness, is $1$. The thickness of the air column is (Refractive index of air $\mu_a = 1.0003$, Wavelength of yellow light in vacuum $\lambda_0 = 6000 \text{ Å}$)