A 12.5 eV electron beam is used to bombard gaseous hydrogen at room temperature. It will emit:

Step-by-step solution

aligned & E = hc = hc E = 6.62 10⁻³⁴ 3 10^8 12.5 1.6 10⁻¹⁹ &=993 ~A ^ & 1 = R ( 1 n ₁^2 - 1 n ₂^2 ) & aligned (where Rydberg constant , R =1.097 10^7 ) or, 1 993 10⁻¹⁰ =1.097 10^7 ( 1 1^2 - 1 n ₂^2 ) Solving we get n ₂=3 Spectral lines Total number of spectral lines =3 Two lines in Lyman series for n ₁=1, n ₂=2 and n ₁=1, n ₂=3 and one in Balmer series for n ₁=2, n ₂=3