Modern Physics Questions

The de-Broglie wavelength of a neutron in thermal equilibrium with heavy water at a temperature $T$ (Kelvin) and mass $m$, is:

The ratio of wavelengths of the last line of Balmer series and the last line of Lyman series is:

The photoelectric threshold wavelength of silver is $3250\times 10^{-10}\text{m}$. The velocity of the electron ejected from a silver surface by ultraviolet light of wavelength $2536\times 10^{-10}\text{m}$ is [Given $h=4.14\times 10^{-15}\text{eVs}$ and $c=3\times 10^8{\text{ms}}^{-1}$ ]: