In photoelectric effect, the stopping potential $\left(\mathrm{V}_0\right) \mathrm{v} / \mathrm{s}$ frequency $(v)$ curve is plotted.

( h is the Planck's constant and $\phi_0$ is work function of metal )

(A) $\mathrm{V}_0 \mathrm{v} / \mathrm{s} v$ is linear.

(B) The slope of $\mathrm{V}_0 \mathrm{v} / \mathrm{s} v$ curve $=\frac{\phi_0}{\mathrm{~h}}$

(C) h constant is related to the slope of $\mathrm{V}_0 \mathrm{v} / \mathrm{s} v$ line.

(D) The value of electric charge of electron is not required to determine h using the $\mathrm{V}_0 \mathrm{v} / \mathrm{s} v$ curve.

(E) The work function can be estimated without knowing the value of $h$.

Choose the correct answer from the options given below :

A small uncharged conducting sphere is placed in contact with an identical sphere but having $4 \times 10^{-8} \mathrm{C}$ charge and then removed to a distance such that the force of repulsion between them is $9 \times 10^{-3} \mathrm{~N}$. The distance between them is (Take $\frac{1}{4 \pi \epsilon_{\mathrm{o}}}$ as $9 \times 10^9$ in SI units)

A long straight wire of a circular cross-section with radius ' a ' carries a steady current I . The current I is uniformly distributed across this cross-section. The plot of magnitude of magnetic field B with distance $r$ from the centre of the wire is given by

The energy E and momentum p of a moving body of mass m are related by some equation. Given that c represents the speed of light, identify the correct equation