The diagram shows the energy levels for an electron in a certain atom. Which transition shown represents the emission of a photon with the most energy?

       
1. \(\mathrm I\)   
2. \(\mathrm{II}\)
3. \(\mathrm{III}\)
4. \(\mathrm{IV}\)

What happens whenever a hydrogen atom emits a photon in the Balmer series?

Ionisation potential of hydrogen atom is 13.6 eV. Hydrogen atoms in the ground state are excited by monochromatic radiation of photon energy 12.1 eV. According to Bohr's theory, the spectral lines emitted by hydrogen will be:

1. two 

2. three

3. four 

4. one

Consider the spectral line resulting from transition \(n=2\) to \(n = 1\) in the atoms and ions given below.  The shortest wavelength is given by: