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The ionization energy of a hydrogen atom is 13.6 eV. If hydrogen atoms initially in the ground state are exposed to monochromatic light of photon energy 12.1 eV, then as per Bohr’s model, how many spectral lines can be produced in the emitted radiation?

1. three
2. four
3. one
4. two

Correct answer: three

Solution

Absorbing 12.1 eV from the ground state lifts the atom to E = -13.6 + 12.1 = -1.5 eV, i.e. n = 3. De-excitation from n = 3 gives 3(3-1)/2 = 3 spectral lines.

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