Which of the following is the radius of the first orbit of $He^{+}$ (in $pm$)?

Number of spectral lines obtained in $He^{+}$ spectra,when an electron makes transition from fifth excited state to first excited state will be

Explain Rutherford's nuclear model of the atom.

The shortest wavelength in the hydrogen spectrum is approximately (in $nm$)

The wavelength of the radiation emitted,when in a hydrogen atom an electron falls from infinity to stationary state $n = 1$,would be ........ $nm$ (Rydberg constant $R_H = 1.097 \times 10^7 \ m^{-1}$)

Which of the following is the energy of a possible excited state of hydrogen? $........... \ eV$