The moment of inertia of thin square plate PQRS of uniform thickness, about an axis passing through centre ' O ' and perpendicular to the plane of the plate is $\left(\mathrm{I}_1, \mathrm{I}_2, \mathrm{I}_3, \mathrm{I}_4\right.$ are respectively the moments of inertia about axis $1,2,3,4$ which are in the plane of the plate as shown in figure)

In hydrogen atom, ratio of the shortest wavelength in the Balmer series to that in the Paschen series is

At certain temperature, $\operatorname{rod} \mathrm{A}$ and $\operatorname{rod} \mathrm{B}$ of different materials have lengths $\mathrm{L}_{\mathrm{A}}$ and $\mathrm{L}_{\mathrm{B}}$ respectively. Their coefficients of linear expansion are $\alpha_A$ and $\alpha_B$ respectively. It is observed that the difference between their lengths remains constant at all temperatures. The ratio $\mathrm{L}_{\mathrm{A}}: \mathrm{L}_{\mathrm{B}}$ is given by

Velocity of light in diamond is $\left(\frac{5}{12}\right)^{\text {th }}$ times that in air. Velocity of light in water is $\left(\frac{3}{4}\right)^{\text {th }}$ times that in air. The angle of incidence of ray of light travelling from water to diamond is (angle of refraction $\left.(\mathrm{r})=30^{\circ}\right)\left[\right.$ Given $\left.\rightarrow \sin 30^{\circ}=\frac{1}{2}\right]$