Q. Ionization potential of hydrogen atom is 13.6 eV. Hydrogen atoms in the ground state are excited by monochromatic radiation of photon energy 12.1 eV. According to Bohr's theory, the spectral lines emitted by hydrogen will be :
A) two
B) three
C) four
D) one
Explanation
[Solution from source] After absorbing 12.1 eV the electron's energy is −13.6 + 12.1 = −1.51 eV, which is the n = 3 level (−13.6/9). From n = 3 the possible downward transitions are 3→2, 3→1 and 2→1, i.e. n(n − 1)/2 = 3 lines. Counting only the direct jump to the ground state would give one line. Answer (2).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.