If the radius of first orbit of hydrogen like ion is $1.763 \times 10^{-2} \mathrm{~nm}$, the energy associated with that orbit (in J ) is

The wavelength of an electron is $10^{3} \mathrm{~nm}$. What is its momentum in $\mathrm{kg} \mathrm{ms}^{-1}$ ? ( $\left.h=6.625 \times 10^{-34} \mathrm{Js}\right)$

The wavenumber of first spectral line of Lyman series of $\mathrm{He}^{+}$ion is $x \mathrm{~m}^{-1}$. What is the wave number ( $\mathrm{in}^{-1}$ ) of second spectral line of Balmer series of $\mathrm{Li}^{2+}$ ion?