An e.m.f. $e=E_0 \cos \omega t$ is applied to a circuit containing $L, C$ and $R$ in series where $X_L=3 R$ and $\mathrm{X}_{\mathrm{C}}=\mathrm{R}$. The average power dissipated in the circuit is

The temperature of an air bubble while rising from bottom to surface of a lake remains constant but diameter is doubled. If pressure on the surface is $h$ meter of mercury column and relative density of mercury is ' $\rho$ ' then the depth of the lake is

The apparent wavelength of light from a star moving away from the earth is $0.02 \%$ more than the actual wavelength. The velocity of star is $\left[\mathrm{c}=\right.$ velocity of light $\left.=3 \times 10^8 \mathrm{~m} / \mathrm{s}\right]$

A parallel plate air capacitor has capacitance $C_P$. It is equally filled with parallel layers of materials of dielectric constants $\mathrm{K}_1$ and $\mathrm{K}_2$. Now its capacity becomes $C_K$. The ratio $C_P$ to $C_K$ is