If $v_0$ is the threshold frequency of a metal $X$, the correct relation between de-Broglie wavelength $(\lambda)$ associated with photoelectron and frequency $(v)$ of the incident radiation is

The difference in radii between fourth and third Bohr orbit of $\mathrm{He}^{+}($in m$)$ is

If $\lambda_0$ and $\lambda$ are respectively the threshold wavelength and wavelength of incident light the velocity of photo electrons ejected from the metal surface is

The energy of third orbit of $\mathrm{Li}^{2+}$ ion (in J ) is