Lines of the $Lyman$ series of the spectrum of hydrogen are in

The energy of one mole of photons of radiation whose frequency is $5 \times 10^{10} \, s^{-1}$ is .......... $J$.

What is the wavelength for a wave having frequency $50 \ Hz$?

Electromagnetic radiation of wavelength $663 \ nm$ is just sufficient to ionise the atom of metal $A.$ The ionization energy of metal $A$ in $kJ \ mol^{-1}$ is ...... .
(Rounded-off to the nearest integer) $\left[ h = 6.63 \times 10^{-34} \ Js, c = 3.00 \times 10^{8} \ ms^{-1}, N_{A} = 6.02 \times 10^{23} \ mol^{-1} \right]$

$A$ photon of wavelength $6630 \mathring{A}$ is incident on a totally reflecting surface. The momentum delivered by the photon is equal to

Find the mass of a photon emitted by a sodium lamp (wavelength $\lambda = 5890 \ \mathring{A}$). How many times is this mass compared to the mass of an electron?