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NEET Physics · Atoms and Nuclei

Bohr model, energy levels and the hydrogen spectrum

Taught in NCERT Class 12 Physics, Chapter 12: Atoms.

3 verified questions: Easy 0 · Medium 2 · NEET level 1

Sample questions

Sample 1Medium

An energy-level diagram for the hydrogen atom shows horizontal lines at n = 1 (−13.6 eV), n = 2 (−3.4 eV), n = 3 (−1.51 eV) and n = 4 (−0.85 eV). An arrow is drawn downward from n = 3 to n = 2. What energy is the emitted photon, and to which series does the line belong?

  1. A

    10.2 eV, Lyman series

  2. B

    1.89 eV, Paschen series

  3. C

    1.51 eV, Balmer series

  4. D

    1.89 eV, Balmer series

Show the answer
The answer is D.

E = −1.51 − (−3.4) = 1.89 eV. Transitions that end on n = 2 form the Balmer series, which lies in the visible region.

  • A.

    10.2 eV is the n = 2 → 1 transition, in the Lyman series.

  • B.

    The energy is right, but the Paschen series ends on n = 3, not n = 2.

  • C.

    1.51 eV is the magnitude of the n = 3 level, not the energy difference.

NCERT: Class 12 Physics, Chapter 12

Sample 2NEET level

Consider the following statements about the Bohr model of the hydrogen atom. 1. The total energy of the electron in the ground state is −13.6 eV. 2. The radius of the nth orbit is proportional to n². 3. The speed of the electron in the nth orbit is proportional to n. 4. The Lyman series lies in the ultraviolet region. Which of the above statements are correct?

  1. A

    1, 2 and 4 only

  2. B

    1 and 2 only

  3. C

    2, 3 and 4 only

  4. D

    1, 2, 3 and 4

Show the answer
The answer is A.

In the Bohr model E_n = −13.6/n² eV and r_n ∝ n², while the speed v_n ∝ 1/n, so statement 3 is false. The Lyman series, transitions ending on n = 1, lies in the ultraviolet.

  • B.

    Leaves out statement 4, which is true: Lyman lines are ultraviolet.

  • C.

    Includes statement 3 and leaves out 1: the speed falls as 1/n, and the ground-state energy is −13.6 eV.

  • D.

    Statement 3 is false: v_n is inversely proportional to n.

NCERT: Class 12 Physics, Chapter 12 (Atoms), Bohr model of the hydrogen atom

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