$A$ plate of refractive index $1.6$ is introduced in the path of light from one of the slits in Young's double slit experiment,then:

Two coherent point sources $S_1$ and $S_2$ vibrating in phase emit light of wavelength $\lambda$. The separation between them is $2 \lambda$ as shown in the figure. The first bright fringe is formed at $P$ due to interference on a screen placed at a distance $D$ from $S_1$ $(D >> \lambda)$. Find the distance $OP$.

$A$ flake of glass (refractive index $\mu = 1.5$) is placed over one of the openings of a double slit apparatus. The interference pattern displaces itself through seven successive maxima towards the side where the flake is placed. If the wavelength of the light used is $\lambda = 600 \, nm$,then the thickness of the flake is ........ $nm$.

In Young's double slit experiment,a glass plate is placed before one slit which absorbs half the intensity of light. Under this case:

In Young's double-slit arrangement,the screen starts moving towards the right with a constant speed $v$. The initial distance between the screen and the plane of the slits is $x$. At $t=0$,the $1^{\text{st}}$ order maxima is located at point $A$. After how much time will the first order minima lie at point $A$?

In a standard $YDSE$ setup,a small transparent slab of thickness $t$ and refractive index $\mu = 1.5$ is placed along the path $AS_2$ (as shown in the figure). Given that the slab thickness $t = d/4$,where $d$ is the slit separation,and the distance from the source $A$ to the slits is not explicitly needed for the shift calculation,find the position of the central maxima on the screen relative to $O$. Assume the distance between the slits and the screen is $D$.