According to the Bohr Theory, which of the following transitions in the hydrogen atom will give rise to the least energetic photon?
1. n = 5 to n = 3
2. n = 6 to n = 1
3. n = 5 to n = 4
4. n = 6 to n = 5

The frequency of radiation emitted when the electron falls from n = 4 to n = 1 in a hydrogen atom will be:
(Given ionization energy of H = 2.18 × 10^–18 J atom ^–1 and h = 6.625 × 10^–34 Js):

1. 1.03 × 10¹⁵ s^–1

2. 3.08 × 10¹⁵ s^–1

3. 2.00 × 10¹⁵ s^–1

4. 1.54 × 10¹⁵ s^–1