First photograph of light as both a particle and wave (2015)

http://m.phys.org/news/2015-03-particle.html

by ThomPete • 10 years ago

139 37 10 years ago

m.phys.org

deckar01• 10 years ago

It took me a few reads for this to sink in.

Quantum interference causes standing waves. Electron-photon particle collisions cause detectable energy release. The particle collisions occur in an interference pattern.

EarthIsHome• 10 years ago

Yes, and the colors describe the speeds of the particles as a result of tbe electron-photon collisions.

It's not necessarily the particles we're seeing, just the particle behaviors from their collisions.

shshhdhs• 10 years ago

This is really cool! What's the reason for the blue & violet colors to be raised more than others in the wave?

Is it just the timing of the snapshot? As in, another picture might show another color at the top of the wave? Or is the standing wave "stuck" in that position?

mdturnerphys• 10 years ago

That's just the color scale they've used for the z axis.

nsxwolf• 10 years ago

It didn't explain the picture.

leksak• 10 years ago

Yeah, I don't know how to interpret it. It's not immediately obvious to me that I'm looking at a wave and particles at the same time.

initram• 10 years ago

Nor does it appear to be a photograph. It looks very much like a 3D rendering with false coloring.

URSpider948• 10 years ago

What the image represents is the energy loss/gain of a whole bunch of electrons that interact one at a time with a light wave traveling along a tiny metal wire (we call this kind of captive light wave a "phonon").

For each electron fired at the wire, it can either pass through unscathed, or it can interact with an electron and scatter off with a different energy, like two billiard balls hitting each other. The collision is fundamentally a collision between two particles. However, the fact that the properties of the collisions vary sinusoidally along the length of the wire imply that the photon is also acting like a wave oscillating up and down the wire.

I disagree that this is the "first time" that we've observed simultaneous wave-particle behavior, you can see the same thing by firing photons at two narrowly-placed slits. This results in a diffraction pattern as if the photons were interfering like waves, but we can confirm that we're detecting single photons at the detector, and you can even confirm that each photon travels through one slit or the other ... See https://en.wikipedia.org/wiki/Double-slit_experiment

_nalply• 10 years ago

Swiss here. The École Polytechnique Fédérale de Lausanne (EPFL), where this experiment has been carried out, is one of the two federal institutes of technology, the other one is the Eidgenössische Technische Hochschule Zürich (ETHZ).

https://en.wikipedia.org/wiki/%C3%89cole_Polytechnique_F%C3%... https://en.wikipedia.org/wiki/ETH_Zurich

emerongi• 10 years ago

It's hard to grasp what was really captured on that image, but this still doesn't rule out the pilot wave theory. I think it's misleading to call it a photograph of light "as both a particle and wave".

posterboy• 10 years ago

Darn the ambiguous english language, do they mean the photograph is a particle-wave? because that wouldn't be a first. /s

msimpson• 10 years ago

This article is much more clear on what the image actually represents: http://www.livescience.com/50019-image-light-wave-particle.h...

"A clever technique and an ultrafast electron microscope have caught an image of light behaving as both particle and wave at the same time. Here, the wave nature is demonstrated in the wavy upper portion, while the particle behavior is revealed below, in the outlines showing energy quantization."

Credit: Fabrizio Carbone/EPFL

Also, this was all published on March 2, 2015.

amelius3• 10 years ago

I have a question about QM, which perhaps somebody here can answer: Is quantization an inherent property of the photon, or is it a property of the material (or of the interaction with it)?

tehwalrus2• 10 years ago

If I remember correctly, quantisation occurs because of the solutions to certain differential equations in the geometry (eg of an atom, of a lasing chamber, etc).

The quantised states are the different solutions to that equation (the different energy levels + spin states in an atom.) - this holds for electrons in atoms being quantised.

The photoelectric effect, which has to do with incident photons, showed that you can't turn up the intensity of long wavelength light and ping electrons off things: the power input didn't change things, but a very low power of short wavelength photons did. Thus, Einstein concluded that there must be something specific about the energy of individual particles, not just the total energy stored in a wave. So it is observed in an interaction, but the information defining the final effect travels with the photon.

pbhjpbhj• 10 years ago

The equations describe reality, they don't form it (so far as we know!).

pitaj2• 10 years ago

I believe that the quantization of the photon is directly related to the idea the electrons can only move between discrete energy levels in their respective atoms.

URSpider948• 10 years ago

The other answers posted here are not quite right. Light energy is indeed inherently quantized, and a photon is one quantum of light. In other words, you can't have a half-photon of light, only even multiples.

Einstein wrote the equation "E = h*(nu)", where h is the so-called "Planck's constant", and nu is the frequency of light. Translated, this means that each photon carries an amount of energy proportional to its frequency, higher-frequency photons (IR -> red -> blue -> UV -> X-ray) carry more energy.

tl;dr: Quantization is an inherent property of light.

DigitalJack• 10 years ago

Do you mean "whole" multiples?

glitchc• 10 years ago

E=h*nu was derived by Max Planck, not Einstein.

amelius3• 10 years ago

E = h*(nu)

Yes, but the question is whether that is due to the material not being able to produce non-quantized photons. Stated differently, suppose we had a different way of generating photons, then could we theoretically create them in a non-quantized way?

jkn• 10 years ago

I don't think this is right. The energy of a photon is h multiplied by the frequency, but the frequency itself can be anything. Even if the process creating the photon is inherently quantized (e.g. bound electron with quantized energy levels), we will measure slightly different frequencies (and so different energies), due for example to the Doppler effect[1]. Still with the Doppler effect, you can give a photon an arbitrary frequency (energy) by changing the velocity of the reference frame where you make the measurement (that is, until someone shows that the velocity of the reference frame is quantized... not something that is presently known).

[1] https://en.wikipedia.org/wiki/Doppler_broadening

mzs• 10 years ago

https://www.eurekalert.org/pub_releases/2015-03/epfd-tfe0301...

Koshkin• 10 years ago

an exchange of energy "packets" (quanta) between electrons and photons

I thought that photons are the energy quanta (that electrons can absorb or lose).

First photograph of light as both a particle and wave (2015)

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