Question

In a sample of H-atoms, electrons de-excite from a level ‘n’ to 1. The total number of lines belonging to Balmer series are two. If the electrons are ionised from level ‘n’ by photons of energy 13 eV. Then the kinetic energy of the ejected photoelectrons will be

• A. 12.15 Ev
• B. 11.49 eV
• C. 12.46 eV
• D. 12.63 eV

Answer 1

Answer: (A)

12.15 Ev

Answer 2

Number of lines in Balmer series = 2.

$\therefore$ n = 4 (lines will be 4 $\rightarrow$ 2, 3$\rightarrow$ 2).

KE of ejected photoelectrons = Ephoton – BEn = 13 – $\frac{13.6}{4^{2}} = 13$ – 0.85 = 12.15 eV.