Which one of the following <strong>correctly</strong> describes the principle of the working of an atomic clock?

  1. A. Vibration of a small quartz crystal
  2. B. Simple harmonic motion of atoms inside a crystal
  3. C. Resonant frequency in cesium (or rubidium) atom
  4. D. Excitation and de-excitation of hydrogen atoms

Correct Answer: C. Resonant frequency in cesium (or rubidium) atom

Explanation

Atomic clocks keep extremely precise time by tracking the resonant frequency of microwave electromagnetic radiation emitted or absorbed by atoms, most commonly cesium or rubidium.

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