एक हाइड्रोजन परमाणु को उसकी मूल अवस्था (ground state) से प्रथम उत्तेजित अवस्था (first excited state) में जाने के लिए आवश्यक ऊर्जा कितनी है?

In the first excited state of a hydrogen atom, the energy of its electron is -3.4 eV. The radial distance of the electron from the nucleus in this state is approximately: (Take 1 eV = 1.6 × 10-19 J, e = 1.6 × 10-19 C, and 14πε0 = 9 × 109 N m2/C2)

The second postulate of Bohr's atomic model (quantization of angular momentum) can be explained on the basis of which theory?