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 $\left.\rightarrow \sin 30^{\circ}=\frac{1}{2}\right]$

When a capacitor is connected in series LR circuit, the alternating current flowing in the circuit

The internal energy of a gas will increase when it

A sonometer wire is stretched by hanging a metal bob, the fundamental frequency of the wire is ' $n_1$ '. When the bob is completely immersed in water, the frequency of vibration of wire becomes ' $n_2$ '. The relative density of the metal of the bob is