That depends on what light you are thinking about. The light from a candle comes from tiny glowing specks of carbon soot heated in the flame.

Lauren Shriver

Electromagnetic radiation is produced or can originate when a charge particle moves in a material with a speed greater than the speed of light in that material but less than the light speed in free space or classical vacuum, thus obeying or not violating Einstein’s second postulate of special relativity, which is itself a special case of the general second postulate of speed limit.

Electromagnetic radiation, which can be heat or visible light or radio waves, can also originate when an electron falls from a higher negative-energy atomic level to a lower negative-energy atomic level in an atom, resulting in an emission of a photon of positive energy having an equivalent positive mass by which spacetime gets curved due to gravity thanks to Einstein’s famous relativistic mass-energy equivalence E = mc2.

Thats a good point. Right now thinking in terms of a universal or original “source” of electromagnetism. But I feel like that isnt very specific. Ill try and get back to you with a more direct version of my question. Im still very new to optics, but I have a gut feeling we are overlooking something fundamental that involves light (hence it generating an personsal research interest, even though my background is in neuriscience).

Lauren Shriver

More really interesting and enjoyable details can be read in the great and recommended book “An Introduction to Classical Electromagnetic Radiation “ by distinguished Professor Emeritus Glenn S. Smith.

Thanks! The title alone has my attention. I'll take the fact that it was recommended to me as a sign to go open up my amazon tab and order it now.

George Dishman you're comment has also made me realize that I don't even remember learning why flames even emit light in the first place. I'll add that to my list of things to review.

In that case Lauren, you should definitely revise black body radiation, cyclotron radiation and Bremsstrahlung, luminescence and phosphorescence, lasers and light emitting diodes. There are many ways to make light, that list is far from exhaustive.

The emmition of EM waves (including light) occures when a medium get excitation from an external source of energy, then it starts to give it back as an EM waves. The emitted EM radiation comes in different frequencies, depend on the type of meduim and the differneces between thier energy levels (orbits of thier electrons), since the radation occures when the electrons turns back to its original energy level after an excitation. The frequency of the emmitted radation can be calculated from E2-E1=fh, where h is Plank’s constant and f is the frequency of the radiated EM wave.

George Dishman I received Glenn S. Smith's book on classical electromagnetic radiation in the mail the other day. The book was a little pricey, but I can already tell this was a good investment! Thanks for the recommendation, its literally the perfect book for my skill level in physics. I really think it will help keep me grounded as I continue to study independently and find a topic to pursue at the universities.

I'm glad you like it Lauren but it was Issam Mohanna who recommended it.

Hi Lauren.

A late answer - sorry

Very specifically light is the energy emitted when an electron moves from a high energy state to a low energy state (a 'cooling' process) That energy is emitted at frequencies related to the band-gap of the electron states and this depends on the materials concerned and the electron shell that emits the energy.

Only a small proportion of the energy is emitted as light (the visible frequencies) the bulk of the energy, in most circumstances is emitted as very low frequency infra-red. which we detect as heat, or more extreme ultra-violet through to gamma ray energy we see from stars.

While it may seem odd that a body producing heat and energy is classed as cooling this is the logical result of energy being radiated away from the hot body.

Ian

Sorry Ian,

IP: Only a small proportion of the energy is emitted as light (the visible frequencies) the bulk of the energy, in most circumstances is emitted as very low frequency infra-red. which we detect as heat ...

That is not correct. When an electron transitions between states in the absence of recoil, the amount of energy carried by the photon is the difference between the energy of the states. Where the emitting particle can recoil, some of the energy is becomes kinetic energy of the particle so the light frequency is slightly reduced but remains the dominant part.

George - I don't disagree with you. My point was intended to look at the macro situation - say in a star or black box radiator.

In this situation the release of energy is largely dominated by statistical variations where the substance emitting the energy, the local pressure and temperature each play a part in determining the frequency of the energy released.

Each specific transaction will, of course, produce unique results.

Ian

Ah, OK Ian. Yes, thermal covers a broad range and for low temperatures, the majority can be in the infrared. Atomic transitions however is quite different, it produces spectral lines where all the energy is at a single frequency. Lauren is just starting studying this topic so the way you expressed it could have been misunderstood.

best regards

George

George Dishman thank you for pointing that out and @Issam Mohanna for your recommendation. Book recommendations are always welcome. Great discussion! These comments will come in handy as I continue to explore this topic.