# Are there sources of light other than the one emitted by electrons? **URL:** \ **Category:** Factual Questions\ **Created:** [August 31, 2018, 12:11pm UTC](https://boards.straightdope.com/t/are-there-sources-of-light-other-than-the-one-emitted-by-electrons/820570 "2018-08-31T12:11:23Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![komolono](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/komolono/32/532_2.png) [@komolono](https://boards.straightdope.com/u/komolono)\ **Post date:** [August 31, 2018, 12:11pm UTC](https://boards.straightdope.com/t/are-there-sources-of-light-other-than-the-one-emitted-by-electrons/820570/1 "2018-08-31T12:11:23Z")
Polarized light - is a reflection always polarized? Depending on your responses I may have more questions (I ponder wheter I have misunderstood something about the nature of light…). ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [August 31, 2018, 12:42pm UTC](https://boards.straightdope.com/t/are-there-sources-of-light-other-than-the-one-emitted-by-electrons/820570/2 "2018-08-31T12:42:17Z")
I assume you are asking whether a reflected light has different polarization than the original light? It depends on the materials, surface structure and incident angle. Metallic mirrors do not appreciably change the polarization (i.e. reflected light has the same polarization as the incident light). Dielectric materials may preferentially reflect one polarization state and transmit the other - which is why the reflection off the surface of water is polarized. This effect is maximized at the [Brewster’s Angle](https://en.wikipedia.org/wiki/Brewster%27s_angle). Of course any coating on the surface can change all this. I’m not sure what this has to do with the source of light being electrons though. Light can be emitted by movement of any charged particle. And gamma rays (which are photons) are emitted by radioactive decay of a nucleus. ---
**Author:** ![komolono](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/komolono/32/532_2.png) [@komolono](https://boards.straightdope.com/u/komolono)\ **Post date:** [August 31, 2018, 12:58pm UTC](https://boards.straightdope.com/t/are-there-sources-of-light-other-than-the-one-emitted-by-electrons/820570/3 "2018-08-31T12:58:59Z")
> [@scr4](#): > > I assume you are asking whether a reflected light has different polarization than the original light? It depends on the materials, surface structure and incident angle. Metallic mirrors do not appreciably change the polarization (i.e. reflected light has the same polarization as the incident light). Dielectric materials may preferentially reflect one polarization state and transmit the other - which is why the reflection off the surface of water is polarized. This effect is maximized at the [Brewster’s Angle](https://en.wikipedia.org/wiki/Brewster%27s_angle). Of course any coating on the surface can change all this. > > I’m not sure what this has to do with the source of light being electrons though. Light can be emitted by movement of any charged particle. And gamma rays (which are photons) are emitted by radioactive decay of a nucleus. What is the source of the sun - electrons, nuclei:confused: ---
**Author:** ![Ruken](https://avatars.discourse-cdn.com/v4/letter/r/f475e1/32.png) [@Ruken](https://boards.straightdope.com/u/Ruken)\ **Post date:** [August 31, 2018, 2:01pm UTC](https://boards.straightdope.com/t/are-there-sources-of-light-other-than-the-one-emitted-by-electrons/820570/4 "2018-08-31T14:01:24Z")
> [@komolono](#): > > What is the source of the sun - electrons, nuclei:confused: Approximately blackbody [thermal radiation](https://en.m.wikipedia.org/wiki/Thermal_radiation). ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [August 31, 2018, 3:41pm UTC](https://boards.straightdope.com/t/are-there-sources-of-light-other-than-the-one-emitted-by-electrons/820570/5 "2018-08-31T15:41:51Z")
The Sun’s atmosphere is a plasma, so it’s mostly electrons (thermal [bremsstrahlung](https://en.wikipedia.org/wiki/Bremsstrahlung)). Protons are much more massive so they don’t move around as much (lower speed _and_ less deflection). That’s not universally true for thermal radiation though. The filament of a light bulb is solid (i.e. atoms), not plasma. Atoms emit light when when an electron drops from a higher energy level to a lower energy level. It’s not really emitted _by_ the electron, it’s emitted by the atom. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [August 31, 2018, 6:10pm UTC](https://boards.straightdope.com/t/are-there-sources-of-light-other-than-the-one-emitted-by-electrons/820570/6 "2018-08-31T18:10:51Z")
> [@scr4](#): > > I assume you are asking whether a reflected light has different polarization than the original light? It depends on the materials, surface structure and incident angle. Metallic mirrors do not appreciably change the polarization (i.e. reflected light has the same polarization as the incident light). . Depends upon what you define as “appreciably”. Metal mirrors certainly do affect the polarization, and if your work requires no change then even that little bit can be a problem. In fact, any reflection that’s not at normal incidence (going smack into the surface) or grazing incidence will have different reflection coefficients for light polarized _in_ the plane of incidence and for light _perpendicular to_ the plane of incidence, and just about any reflection thus changes the polarization state of the light. Have a look at Born and Wolf’s _Principles of Optics_ ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [August 31, 2018, 6:27pm UTC](https://boards.straightdope.com/t/are-there-sources-of-light-other-than-the-one-emitted-by-electrons/820570/7 "2018-08-31T18:27:08Z")
> [@CalMeacham](#): > > Depends upon what you define as “appreciably”. Metal mirrors certainly do affect the polarization, and if your work requires no change then even that little bit can be a problem. Yes it’s definitely measurable. I should have said it’s not significant to the extent that you’d see a difference by looking at it with polarizing sunglasses. My group has built two spectropolarimeters for observing the Sun, and we always have to make sure our feed telescope is perfectly axially symmetric so it doesn’t introduce any spurious polarization. ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [August 31, 2018, 11:44pm UTC](https://boards.straightdope.com/t/are-there-sources-of-light-other-than-the-one-emitted-by-electrons/820570/8 "2018-08-31T23:44:42Z")
Hawking radiation from black holes includes light, so there’s one non-electron source. Although I understand it would have to be an asteroid-mass black hole for the light to be in the visible range (more mass and it’d be emitting in the infrared or radio wavelengths, less mass and it would be ultraviolet or higher). ---
**Author:** ![octopus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/octopus/32/3716_2.png) [@octopus](https://boards.straightdope.com/u/octopus)\ **Post date:** [September 1, 2018, 1:03am UTC](https://boards.straightdope.com/t/are-there-sources-of-light-other-than-the-one-emitted-by-electrons/820570/9 "2018-09-01T01:03:30Z")
Anti-matter and matter reaction should produce light of some wavelength. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [September 1, 2018, 1:04am UTC](https://boards.straightdope.com/t/are-there-sources-of-light-other-than-the-one-emitted-by-electrons/820570/10 "2018-09-01T01:04:30Z")
Black holes are (unsurprisingly) blackbodies, so one that’s smaller (and hence hotter) would still emit more photons across the whole spectrum. The peak would be higher frequency, but that would just mean that you’d sunburn before you had a chance to broil. EDIT: > [@](#): > > Anti-matter and matter reaction should produce light of some wavelength. Mostly just from positrons and electrons, at least proximately, which is really still just from electrons, since positrons are (in a sense) the same thing. Though you’ll still get a few quark-photon interactions from pi0 decays. ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [September 2, 2018, 12:23am UTC](https://boards.straightdope.com/t/are-there-sources-of-light-other-than-the-one-emitted-by-electrons/820570/11 "2018-09-02T00:23:10Z")
Čerenkov Radiation from Protons. [Phys. Rev. 84, 181 (1951) - \ifmmode \check{C}\else \v{C}\fi{}erenkov Radiation from Protons and the Measurement of Proton Velocity and Kinetic Energy](https://journals.aps.org/pr/abstract/10.1103/PhysRev.84.181) ---
**Author:** ![Textual\_Innuendo](https://avatars.discourse-cdn.com/v4/letter/t/898d66/32.png) [@Textual\_Innuendo](https://boards.straightdope.com/u/Textual_Innuendo)\ **Post date:** [September 8, 2018, 1:00pm UTC](https://boards.straightdope.com/t/are-there-sources-of-light-other-than-the-one-emitted-by-electrons/820570/12 "2018-09-08T13:00:02Z")
It’s been a long time since I read Weinberg’s The First Three Minutes, but is there any “primordial” light originating from the energy from the big bang itself? If I recall (probably incorrectly), some of this energy was banging around as gamma radiation at first, then the universe cooled enough to be transparent, and then it was light, ultimately turning into the cosmic background radiation. Or am I mistaken about that? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [September 8, 2018, 1:29pm UTC](https://boards.straightdope.com/t/are-there-sources-of-light-other-than-the-one-emitted-by-electrons/820570/13 "2018-09-08T13:29:36Z")
In the beginning, everything was just a general mishmash of stuff. It’s tough to say what particular sort of particles any other particular sort of particles came from.