A coil has inductance H . The ratio of its reactance when it is connected first to an a.c. source and then to d.c. source is

A particle of mass m collides with another stationary particle of mass $M$. The particle $m$ stops just after collision. The coefficient of restitution is

In the circuit shown in the following figure, the potential difference cross $3 \mu \mathrm{~F}$ capacitor is

Sodium light $\left(\lambda=6 \times 10^{-7} \mathrm{~m}\right)$ is used to produce interference pattern. The observed fringe width is 0.12 mm . The angle between the two wave trains is