I always have a doubt when someone says that light is emitted by only certain transitions of electron but not by all of them. If an electron jumps from a higher energy orbit to a low energy orbit, is the energy difference released only in the form of a photon packet or does it release in any other forms of energy? Now, I say that a material can emit light in so and so wavelength, does it mean that the object is transparent to those wavelengths and other wavelengths are just absorbed to generate heat?

  • $\begingroup$ Hi, you could cite your source : always have a doubt when someone says that light is emitted by only certain transitions of electron but not by all of them. thanks $\endgroup$ – user108787 Oct 31 '16 at 12:33
  • $\begingroup$ There, I was talking about a general convention that only some of the transitions of the electron emit light and others do not. Which is perhaps the reason why led has a sharper wavelength of light compared to a bulb. $\endgroup$ – lattitude Oct 31 '16 at 12:35
  • $\begingroup$ "Transitions" of electrons apply to atomic energy levels. But in a sense something similar happens in LEDs. Incandescent bulbs on the other hand make use of black-body radiation, not transitions. $\endgroup$ – Andras Deak Oct 31 '16 at 12:41
  • $\begingroup$ Here I am having a doubt regarding the emission of light by atoms. Can you please explain how only certain transitions give light and others are converted into heat? $\endgroup$ – lattitude Oct 31 '16 at 12:44

The energy freed by the transition from a higher to a lower energy state can be released by various other mechanisms (which observe conservation laws) in addition to the emission of a photon. An example is the Auger effect, where the energy is released by the kinetic energy of another emitted electron. In solids (semiconductors), the transition energy is often released by a photon plus a phonon which is necessary for momentum conservation.

Postscript: Upon suggestion of @CountTo10 I add some links I have found. Here a lecture on radiative transitions mentioning also some non-radiative ones in gases https://legacy.wlu.ca/documents/37121/NotesCh4.pdf



  • $\begingroup$ +1 if there was ever an answer to be expanded on, this is the one. How many are told ... photon in followed by photon out. E and p are conserved and that's it. Even a few links to other processes would be very helpful. $\endgroup$ – user108787 Oct 31 '16 at 14:40

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