The value of planck's constant, if the slope of the graph of stopping potential versus frequency of incident light is $4 \times 10^{-15} \mathrm{~V}$-s is (given charge of an electron $=1.6 \times 10^{-19} \mathrm{C}$ )

For photoelectric effect which of the following statements are true. (I) The kinetic energies of the photoelectrons do not depend on the frequency of light. (II) Photoelectric effect will always occur for highly intense light. (III) The maximum kinetic energy of photoelectron does not depend upon the intensity of the light. (IV) The escaping electron's kinetic energy is larger for larger frequency.

Which of the following statements is not true?

The light emitted in the transition $n=3$ to $n=2$, (where $n$ is the principal quantum number of the state) in hydrogen is called $\mathrm{H}_\alpha$-light. Find the maximum work function that a metal can have, so that $\mathrm{H}_\alpha$-light can emit photoelectrons from it.