Two coherent sources whose intensity ratio is $64: 1$ produce interference fringes. The ratio of intensities of maxima and minima is

$A$ 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 $\pi$)

The ratio of maximum to minimum intensity in an interference pattern is $25 : 16$. Calculate the ratio of maximum to minimum amplitude.

If the amplitude ratio of two sources producing interference is $3:5$,the ratio of intensities at maxima and minima is

The path difference between two interference waves at a point on a screen is $11.5 \lambda$. The point is

Two monochromatic light beams have intensities in the ratio $1 : 9$. An interference pattern is obtained by these beams. The ratio of the intensities of maximum to minimum is (in $: 1$)