# Light --- Is it really a wave? **URL:** \ **Category:** Factual Questions\ **Created:** [July 5, 2003, 4:52am UTC](https://boards.straightdope.com/t/light-is-it-really-a-wave/186348 "2003-07-05T04:52:01Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Major\_Kong](https://avatars.discourse-cdn.com/v4/letter/m/b9bd4f/32.png) [@Major\_Kong](https://boards.straightdope.com/u/Major_Kong)\ **Post date:** [July 5, 2003, 4:52am UTC](https://boards.straightdope.com/t/light-is-it-really-a-wave/186348/1 "2003-07-05T04:52:01Z")
Is light realty a wave? I have been reading Richard Feynman’s “QED”, were he seems to make the case light is not wave, but is instead a only a particle, but a particle that we cannot predict the movements of? So is light really a wave? Or just a particle that we cannot predict the movements of, so it appears a like a wave? ---
**Author:** ![Major\_Kong](https://avatars.discourse-cdn.com/v4/letter/m/b9bd4f/32.png) [@Major\_Kong](https://boards.straightdope.com/u/Major_Kong)\ **Post date:** [July 5, 2003, 4:53am UTC](https://boards.straightdope.com/t/light-is-it-really-a-wave/186348/2 "2003-07-05T04:53:02Z")
Please forgive my grammar mistakes. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [July 5, 2003, 4:57am UTC](https://boards.straightdope.com/t/light-is-it-really-a-wave/186348/3 "2003-07-05T04:57:37Z")
It’s a wave and a particle…or it’s neither. The way I understand it is light can be considered a wave or a particle depending on how you look at it. Do one type of experiment and it is useful to think of it as a particle. Do a different experiment and it is useful to consider it a wave. In reality it is likely something else we don’t have a definition for that looked at different ways shows different aspects. Consider a pyramid glued to a cube. Looked at one way you see the pyramid, looked at another you see a cube but taken in totality it’s not really a cube or a pyramid. Unfortunately we can’t seem to grasp the ‘bigger’ picture in one go and only see one or the other given aspect. ---
**Author:** ![Major\_Kong](https://avatars.discourse-cdn.com/v4/letter/m/b9bd4f/32.png) [@Major\_Kong](https://boards.straightdope.com/u/Major_Kong)\ **Post date:** [July 5, 2003, 5:00am UTC](https://boards.straightdope.com/t/light-is-it-really-a-wave/186348/4 "2003-07-05T05:00:04Z")
But is light really a wave? Or just a wave of probability? Meaning you cannot predict the movement of the “particle” light? ---
**Author:** ![Jon\_the\_Geek](https://avatars.discourse-cdn.com/v4/letter/j/bbce88/32.png) [@Jon\_the\_Geek](https://boards.straightdope.com/u/Jon_the_Geek)\ **Post date:** [July 5, 2003, 5:31am UTC](https://boards.straightdope.com/t/light-is-it-really-a-wave/186348/5 "2003-07-05T05:31:02Z")
As far as we understand it, everything is both _really_ a wave and _really_ a particle… meaning, as Whack-a-Mole described, we probably don’t _really_ understand what’s going on. Light has particle properties in some experiments (for example, light seems to transfer energy in discreet packets, so it must come in particle form, ie photons). In other experiments, light is definitely a wave (thin slit interference, for example, where light can be made to interfere with itself–something a pure particle, even one described by a probability wave function, shouldn’t do). The same can technically be said for everything. For example, Jupiter is technically a wave in some observations… it just has a wavelength much smaller than Jupiter itself, so it generally acts a whole lot more like a particle. You are also a wave (or a collection thereof), you just have a very small wavelength, so you appear to be in one place at any given time. I’ll let someone else step in with deBroglie info–I don’t have the formulae handy to do the subject justice. ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [July 5, 2003, 5:34am UTC](https://boards.straightdope.com/t/light-is-it-really-a-wave/186348/6 "2003-07-05T05:34:58Z")
You should read **Chronos** ’s article: [How can light be both a wave and a particle?](http://www.straightdope.com/mailbag/mlightwaveparticle.html) And the endless debate in COSR that followed. ---
**Author:** ![Major\_Kong](https://avatars.discourse-cdn.com/v4/letter/m/b9bd4f/32.png) [@Major\_Kong](https://boards.straightdope.com/u/Major_Kong)\ **Post date:** [July 5, 2003, 5:48am UTC](https://boards.straightdope.com/t/light-is-it-really-a-wave/186348/7 "2003-07-05T05:48:44Z")
Yeah, but I see Chronos’ article in complete contradiction with Feynamen, ---
**Author:** ![Major\_Kong](https://avatars.discourse-cdn.com/v4/letter/m/b9bd4f/32.png) [@Major\_Kong](https://boards.straightdope.com/u/Major_Kong)\ **Post date:** [July 5, 2003, 5:50am UTC](https://boards.straightdope.com/t/light-is-it-really-a-wave/186348/8 "2003-07-05T05:50:16Z")
Or Feynman. ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [July 5, 2003, 6:13am UTC](https://boards.straightdope.com/t/light-is-it-really-a-wave/186348/9 "2003-07-05T06:13:02Z")
Here are the two COSR threads: [How can light be both a wave and a particle?](http://boards.straightdope.com/sdmb/showthread.php?s=&threadid=174687) [particle and wave???](http://boards.straightdope.com/sdmb/showthread.php?s=&threadid=174692) ---
**Author:** ![Bill\_H](https://avatars.discourse-cdn.com/v4/letter/b/a5b964/32.png) [@Bill\_H](https://boards.straightdope.com/u/Bill_H)\ **Post date:** [July 5, 2003, 6:41am UTC](https://boards.straightdope.com/t/light-is-it-really-a-wave/186348/10 "2003-07-05T06:41:27Z")
**Major Kong** wrote > [@](#): > > Yeah, but I see Chronos’ article in complete contradiction with Feynamen. As one who is impressed with both of these gentlemen (I named my son after one of them; I’ll leave you to guess which one), I’m curious to hear **Chronos** ’s thoughts on this. ---
**Author:** ![Scarf-Ace](https://avatars.discourse-cdn.com/v4/letter/s/bc79bd/32.png) [@Scarf-Ace](https://boards.straightdope.com/u/Scarf-Ace)\ **Post date:** [July 5, 2003, 3:15pm UTC](https://boards.straightdope.com/t/light-is-it-really-a-wave/186348/11 "2003-07-05T15:15:05Z")
Perhaps light is an energy wave that charges latent particles in the “quantuum foam” which then become “photons”. I’m just speculating of couse. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [July 5, 2003, 3:55pm UTC](https://boards.straightdope.com/t/light-is-it-really-a-wave/186348/12 "2003-07-05T15:55:11Z")
Kong: How many wave/particle threads do you need to start on this board, buddy?🙂 Look, light is not a wave or a particle. It’s that simple. In order to understand and predict the behavior of light, we need to assign it certain properties. It appears to behave **like** a wave in some circumstances and **like** a particle in others. We are projecting a macroscopic model on something that is below the physical limits of our senses. Light is Light. And this goes for any of the various particles described in modern physics. Electrons, or what-have-you. ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [July 5, 2003, 4:16pm UTC](https://boards.straightdope.com/t/light-is-it-really-a-wave/186348/13 "2003-07-05T16:16:38Z")
The thing you have to understand is that very small and very large objects are not like the objects we encounter on a day-to-day basis. Light is like nothing we’re familiar with, and the wave-particle duality is the result of our trying to fit it into categories that it doesn’t belong in. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [July 5, 2003, 4:36pm UTC](https://boards.straightdope.com/t/light-is-it-really-a-wave/186348/14 "2003-07-05T16:36:58Z")
Consider this old fable: > [@](#): > > A group of blind men walking through the savannah run into an elephant. Never having encountered one of these before they start trying to determine what it is. > > One blind man feels the leg and declares the elephant is really a tree. > > Another blind man grabs the trunk and declares the elephant must be a snake of some sort. > > A third blind man grabs the tail and decideds the elephant must be a length of rope. (NOTE: I did that from memory so no cite and apologies if I mussed it up a bit but I think the sense of it stands) In the wave/particle duality of light we are essentially the blind men fumbling at different parts of the elephant and grasping at different aspects of it to determine what it is yet unable to grasp the greater reality of the elephant in its entirety. ---
**Author:** ![Foolonthehill](https://avatars.discourse-cdn.com/v4/letter/f/e274bd/32.png) [@Foolonthehill](https://boards.straightdope.com/u/Foolonthehill)\ **Post date:** [July 5, 2003, 5:15pm UTC](https://boards.straightdope.com/t/light-is-it-really-a-wave/186348/15 "2003-07-05T17:15:16Z")
“At the speed light travels, it’s a good thing it don’t weigh much.” - Hollywood George, c. 1969. ---
**Author:** ![Ring](https://avatars.discourse-cdn.com/v4/letter/r/6a8cbe/32.png) [@Ring](https://boards.straightdope.com/u/Ring)\ **Post date:** [July 5, 2003, 6:29pm UTC](https://boards.straightdope.com/t/light-is-it-really-a-wave/186348/16 "2003-07-05T18:29:18Z")
Maxwell’s equations like Newton’s laws are excellent approximations, but when you get into things like black body radiation, the photoelectric effect, Compton scattering etc. they cease to cut the mustard. First Planck and then Einstein discovered that in order to explain these phenomenon you had to posit that only discrete amounts of energy equal to integer values of h\*f (Planck’s constant times the frequency) could be exchanged with resonators (matter). And thus was born quantum mechanics. You can relate light quanta to an electromagnetic wave by considering that the probability per unit time that a photon will be detected in any small volume is proportional to the square of the amplitude of the wave’s electric field vector. ---
**Author:** ![Major\_Kong](https://avatars.discourse-cdn.com/v4/letter/m/b9bd4f/32.png) [@Major\_Kong](https://boards.straightdope.com/u/Major_Kong)\ **Post date:** [July 7, 2003, 4:32am UTC](https://boards.straightdope.com/t/light-is-it-really-a-wave/186348/17 "2003-07-07T04:32:47Z")
> [@](#): > > Look, light is not a wave or a particle. It’s that simple. In order to understand and predict the behavior of light, we need to assign it certain properties. It appears to behave like a wave in some circumstances and like a particle in others. We are projecting a macroscopic model on something that is below the physical limits of our senses. > > Light is Light. > > And this goes for any of the various particles described in modern physics. Electrons, or what-have-you. But if I am reading Feynman correctly, he seems to be saying that photons (light) are particles. And all their behavior can be described treating them as particles. It is just in the macroscopic world the “paths” of the particles will cancel out all but one path, which isn’t true for photons, electrons, etc. But photons are definitely particles. ---
**Author:** ![CurtC](https://avatars.discourse-cdn.com/v4/letter/c/ce73a5/32.png) [@CurtC](https://boards.straightdope.com/u/CurtC)\ **Post date:** [July 7, 2003, 4:49am UTC](https://boards.straightdope.com/t/light-is-it-really-a-wave/186348/18 "2003-07-07T04:49:02Z")
The idea that I’ve settled on is that thinking of it as a “probability wave” is most comfortable for me. The photon (or electron, or Jupiter, or whatever particle) exists as a probability wave between the times when we observe it as a particle. Is this generally correct? If it’s not, do I miss out on anything by thinking this way? ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [July 7, 2003, 4:55am UTC](https://boards.straightdope.com/t/light-is-it-really-a-wave/186348/19 "2003-07-07T04:55:01Z")
> [@](#): > > \*Originally posted by Major Kong \* > **But if I am reading Feynman correctly, he seems to be saying that photons (light) are particles.** It’s just a metaphor. A classical particle is something whose behavior can be explained by Newton’s laws. Photons are definitely not classical particles. You can think of photons as particles with some wave-like attributes such as phase and interference, which is what Feynman is doing. It’s equally correct to think of them as waves with some particle-like attributes (quantization). The truth is that neither analogy/metaphor is perfect. Why is it so hard to accept that classical/macroscopic ideas like “particles” and “waves” do not apply to photons and subatomic particles? It’s like debating whether SUVs are trucks or cars. You are trying to apply outdated classification schemes to newly discovered (or invented) things, and it’s not going to work. ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [July 7, 2003, 5:00am UTC](https://boards.straightdope.com/t/light-is-it-really-a-wave/186348/20 "2003-07-07T05:00:15Z")
I like the SUV analogy, **scr4**. 🙂 [Next page](https://boards.straightdope.com/t/light-is-it-really-a-wave/186348.md?page=2)