When a light wave undergoes reflection at the interface from air to glass,the change in phase of the reflected wave is equal to

The displacements of two interfering light waves are given by $y_1 = 4 \sin \omega t$ and $y_2 = 3 \sin (\omega t + \frac{\pi}{2})$. What is the amplitude of the resultant wave?

Two monochromatic coherent light beams $A$ and $B$ have intensities $L$ and $\frac{L}{4},$ respectively. If these beams are superposed, the maximum and minimum intensities will be

If $\frac{\text{Path difference}}{\text{Wave length}} = n$ (where $n$ is an integer),what kind of interference is formed?

Two coherent sources $S_1$ and $S_2$ and a screen are arranged as shown in the figure. If the distance between the two coherent sources is $n \lambda$ and the distance of the screen from the nearer coherent source $S_2$ is $D$,then the distance of the first bright fringe on the screen from the point $O$ is (where $\lambda$ is the wavelength of the light emitted by the coherent sources).

The frequency of a light ray having a wavelength of $3000 \ \mathring A$ is