An inductance of $\frac{200}{\pi} \ mH$,a capacitance of $\frac{10^{-3}}{\pi} \ F$ and a resistance of $10 \ \Omega$ are connected in series with an $AC$ source of $220 \ V, 50 \ Hz$. The phase angle of the circuit is:

If $|a|=1, |b|=2$ and the angle between $a$ and $b$ is $120^{\circ}$,then ${(a+3b) \times (3a-b)}^2$ is equal to

$A$ ray of light is incident normally on a glass slab of thickness $5 ~cm$ and refractive index $1.6$. The time taken by a ray to travel from the source to the surface of the slab is the same as the time taken to travel through the glass slab. The distance of the source from the surface is (in $~cm$)

What is the pressure on a swimmer $20 \, m$ below the surface of water in $atm$?

$A$ plano-convex lens fits exactly into a plano-concave lens. Their plane surfaces are parallel to each other. If the lenses are made of different materials with refractive indices $\mu_1$ and $\mu_2$ and $R$ is the radius of curvature of the curved surface of the lenses,then the focal length of the combination is

In which of the following compounds is the transition metal in oxidation state zero?