# Light is both a wave and a particle?

Discussion in 'Archived Threads 2001-2004' started by Colin Dunn, Apr 26, 2002.

1. ### Colin Dunn Supporting Actor

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Over in the thread about Algebra II, many people working in scientific/technical fields have demonstrated how mathematics - even abstract concepts like imaginary/complex numbers - is used in their professions.

Now it's my turn to pose a question. In high school physics, I was told that light is both a wave and a particle. When dealing with light, theories and calculations for both waves and particles are used.

But how can it be both? After all, a wave is a form of energy moving through a medium (which is itself composed of matter); a particle is a tiny piece of matter (a molecule, an atom, or a subatomic particle).

So does that imply that light is both matter and energy? How is this possible? Or is that a discovery that a future Nobel Prize winner will have to make???

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I'm of the opinion that physicists describe light as both a wave and a particle because they have no better way to describe it--they do not fully understand its true nature. I think you're right--it's some third type that no one has yet been able to adequately characterize.

3. ### Andrew W Supporting Actor

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You were misinformed or weren't paying close attention.

Light has both wave and particle characteristics and you use to correct calculations depending upon the property you will to use. But is is not matter. It would then take an infinite amount of energy to bring it up to C.

4. ### Adil M Supporting Actor

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Nice job, Einstein.
I'm a nerd.

5. ### BrianW Cinematographer

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Colin, I know this doesn’t sound like a reasonable answer, but it’s possible because it just is. And it’s not only light (photons), but every subatomic particle. Even protons and neutrons with their relatively high rest masses (photons have no rest mass, as Andrew points out, so they can be, well, light) behave like waves that are best represented by quantum statistical equations. We’ve seen even these heavy particles tunnel through energy barriers that would be impossible for solid matter to penetrate. This is analogous to a diamond locked in a safe suddenly disappearing and reappearing on the outside without opening the safe. In fact, this is more than an analogy: It’s exactly the same thing. There is a non-zero probability that a diamond in a safe could actually exhibit this very behavior through quantum tunneling of all its particles at once. Though, truth be told, it is very unlikely that this has ever happened anywhere in the universe since the beginning of time. But in about a thousand billion years, it’s likely that the occurrence of an object as big as a diamond tunneling through a barrier and remaining intact will have become a certainty at least once during the universe’s existence.

We think of very small things as just that – very small things. But subatomic particles are not just tiny billiard balls. You’d think that because we exhibit the properties of solid matter that we’d be made up of even smaller particles of matter that exhibit the same properties. But that’s just not the case. We’re made up of probabilities of existence, and what we perceive as solidity is simply the covalent and electromagnetic interaction between the particles (that are often anything but) from which we are built.

It’s a completely different world down there on the subatomic level. We first approach that subatomic world with a classical interpretation (particles with mass and velocity) because that’s what we experience on our scale of existence. But as we learn more, we must dismiss the notion that particles are just tiny billiard balls and embrace the notion that they are manifestations of probability curves, the outskirts of which produce some very surprising and counter-intuitive realities.

6. ### Mary M S Screenwriter

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7. ### Randy Tennison Screenwriter

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Light . . . Wave . . . Particle . . .Sprinkle . . . Donut . . Hole . . . Deep . . . Dark . . . Light

It's a giant circle!

Umm, donuts. Gotta go!

8. ### DaveF Moderator Moderator

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"How can it be" is a question often not answered by science. But, it be.
Light behaves like rays at a macroscopic level (when all the objects are much larger than the optical wavelength). Reflections from mirrors, magnifying glasses, camera lenses, and rainbows can all be described well using the ray approach.
But when the light has some coherence (lasers are coherent), then the wave nature is easily seen. Rainbows in oil slicks are described with the help of the waves. Also, polarizing sunglasses show aspects of the wave nature. And the twinkling of stars is also evidence of light as a wave. And holograms are one of the coolest uses of light-as-wave.
Light can also be described as a particle (photon). A photon is packet of energy, and describe the discrete nature of light. It's not necessarily continuous (always on). Rather, light arrives in little bundles. If you're working with extremely low-light levels, then these photons become more apparent. There's an area of measurement involving "Photon counting", with the measurements involving just 100's of photons / sec in the measurements. The green phosphor screen of older Oscilloscopes can be described via the particle (photon) scheme. I think night-vision goggles also involves the particle aspect of light.
Hopefully that makes some small bit of sense. If not, I'll clarify when I'm awake
if you work with coherent sources (lasers), you will most likely need to then it quickly becomes important to describe wave
Light was first, I believe, described in geometric ways. Reflections, refraction (your pencil looks bent when you put in water) follow simple geometric rules.
Later ca. 1800s, it there were various bits of experimental data that could not be readily explained using the ray/geometry scheme. I think it was Fraunhofer who first convincingly argued that light was a wave.

9. ### Chu Gai Lead Actor

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10. ### AviTevet Stunt Coordinator

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Well, one problem with definitively identifying the true nature of light is that interaction with it changes its behavior. That's why when you run an experiment that attempts to quantify light as a particle, you get particle results, but when you run an experiment to quantify light as a wave, you get wave results.

11. ### AaronNWilson Second Unit

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Thanks for the link Chu, I feel slightly smarter now .

12. ### Ashley Seymour Supporting Actor

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