Question

A 12.5 eV electron beam is used to bombard gaseous hydrogen at room temperature. What series of wavelength will be emitted?

Answer 1

First excitation energy

E = E₂ – E₁ = -3.4 – (-13.6) = 10.2 eV

Second excitation energy

E = E₃ – E₁ = -1.51 -(-13.6) = 12.09 eV

Third excitation energy

E = E₄ – E₁ = -0.85 – (-13.6) = 12.75 eV

Second incident beam has energy = 12.5 eV So only first two lines in the Lyman series of wave-length 103 nm and 122 nm will be emitted.

Also E₃ – E₂ = -1.51 – (-3.4) = 4.91 eV

i.e, first line in the Balmer series of wavelength 656 nm will also be emitted