The de-Broglie wavelength of an electron in the third Bohr orbit of H -atom is

The wavenumber of the first line $\left(n_2=3\right)$ in the Balmer series of hydrogen is overline $\bar{v}_1 \mathrm{~cm}^{-1}$. What is the wavenumber (in $\mathrm{cm}^{-1}$ ) of the second line ( $n_2=4$ ) in the Balmer series of $\mathrm{He}^{+}$?

Which of the following sets of quantum numbers is not possible for the electron?

The uncertainty in the position of electron $(\Delta x)$ is approximately 100 pm . The uncertainty in momentum (in $\mathrm{kg} \mathrm{ms}^{-1}$ ) of an electron $\left[h=6.626 \times 10^{-34} \mathrm{Js}\right]$