The value of the energy for the first excited state of hydrogen atom will be $............. \ eV$.

The energy of the second Bohr orbit of the hydrogen atom is $-3.4 \ eV$. The energy of the fourth Bohr orbit of the $He^{+}$ ion will be: (in $eV$)

When an electron transitions from $n = 4$ to $n = 2$,the emitted spectral line will be ........

The energy difference of two stable orbits of Hydrogen is $214.68 \ kJ \ mol^{-1}$. If the transition of an electron takes place,find the emitted frequency. (Note: $v = \Delta E/h$ and $h = 6.626 \times 10^{-34} \ J \ s$)

If a hydrogen atom is excited by an energy of $8.4 \ eV$,what will be the number of spectral lines emitted?

Time taken for an electron to complete one revolution in the Bohr orbit of hydrogen atom is