A light wave travels through three transparent materials of equal thickness. Rank in order, from the highest to lowest, the indices of refraction $n_1,n_2$ and $n_3$.

Two are mirror are inclined at an angle $\mathrm{\theta }$ is shown in figure. Light ray is incident parallel to one of the mirror. The ray will start retracting its path after third reflection if

As shown in the figure a particle is placed at $\mathrm{O}$ in front of a plane mirror $\mathrm{M}.\mathrm{A}$ man at $\mathrm{P}$ can move along path $\mathrm{PY}$ and $\mathrm{PY}\text{'}$ then which of the following is true?

A light ray $\mathrm{I}$ is incident on a plane mirror $\mathrm{M}$. The mirror is rotated in the direction as shown in the figure by an arrow at frequency $\frac{9}{\pi } \mathrm{rev} {\mathrm{s}}^{-1}$. The light reflected by the mirror is received in the wall $\mathrm{W}$ at a distance $10 \mathrm{m}$ from the axis of rotation. When the angle of incidence becomes $37°$ the speed of the spot (a point) on the wall is:

Shown plane mirror is lying in $\mathrm{y}-\mathrm{z}$ plane. A particle $\mathrm{P}$ has velocity $\overrightarrow{\mathrm{u}}=5\hat{\mathrm{i}}+6\hat{\mathrm{j}}$ at $\mathrm{t}=0$ & acceleration $\overrightarrow{\mathrm{a}}=2\mathrm{t}\hat{\mathrm{j}}$. velocity of its image at $\mathrm{t}=2\mathrm{s}$ relative it is 

There are two plane mirror with reflecting surfaces facing each other. Both the mirror are moving with speed $\mathrm{v}$ away from each other. A point is placed between the mirror. The velocity of the image from due to n-th reflection will be-