The frequency of a light wave with a wavelength of $500 \, \mathring A$ is $....... \, Hz$.

Two waves having amplitudes in the ratio $5:1$ produce interference. The ratio of the maximum to minimum intensity 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 path difference between two interference waves at a point on a screen is $11.5 \lambda$. The point is

The phenomenon of interference is shown by

$A$ beam with wavelength $\lambda$ falls on a stack of partially reflecting planes with separation $d$. The angle $\theta$ that the beam should make with the planes so that the beams reflected from successive planes may interfere constructively is (where $n = 1, 2, \dots$)