Bohr postulated that the angular momentum of an electron in an allowed orbit is
Correct answer: B. an integral multiple of h divided by 2 pi
- A. any value at all
- B. an integral multiple of h divided by 2 pi
- C. always zero
- D. equal to hf
Explanation
Quantising angular momentum in units of h over 2 pi is what restricts the electron to particular orbits and therefore particular energies, and de Broglie later showed this is the condition for a whole number of electron wavelengths to fit round the orbit. Without the postulate, classical physics predicts the electron should spiral into the nucleus. It was an assumption Bohr made because it reproduced the observed spectrum.
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Atoms emit or absorb light at specific wavelengths because electrons occupy quantized energy levels and change levels by absorbing or releasing photons. The topic covers emission and absorption spectra, spectral series, hydrogen’s line spectrum, energy-level transitions, and the relation between wavelength, frequency and photon energy.
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