To determine the wavelength

Question

A 12.5 eV electron-beam is used to excite a gaseous hydrogen atom at room temperature. Determine the wavelength and the corresponding series of lines emitted.

Answer 1

The wavelength of emitted series is 99.2nm and this belongs to the Lyman series of Bohr's Hydrogen spectrum.
The wavelength of series emitted during transition is given by the formula.
hc/E=1
E=12.5eV
hc=1240eV
Therefore wavelength of emitted series is:
I=1240/12.5=99.2nm
This belongs to the Lyman series of Bohr's Hydrogen spectrum.