Question

Three photons coming from emission spectra of hydrogen sample are picked up. Their energies are $12.1eV,10.2eV$ and $1.9eV$ . These photons must come from

• A. a single atom
• B. two atoms
• C. three atom
• D. either two atoms or three atoms

Answer 1

The correct option is D either two atoms or three atoms

These energies are due the hydrogen electron dropping down from a higher excited energy level to a lower level .. so they must each be photons from a single atom (electrons don't move between atoms when they change energy levels)
12.1eV .. emitted when an electron drops from level n=3 (1.51 eV) to n=1 (13.60eV)
[excess energy 13.6 - 1.51 = 12.09eV]
10.2 eV .. emitted for a transition between n=2 (3.4eV) and n=1 (13.6eV)
1.9eV .. emitted for a transition between n=3 (1.51eV) and n=2 (3.40eV)