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In Reply to: RE: The Double-Slit experiment posted by tunenut on August 19, 2015 at 15:12:19
You wrote,
"The strange finding of quantum mechanics is that a quanta does not behave either as a particle or as a wave, but has characteristics of both. A quanta could be a photon of light or an electron, or something else small, either with or without mass."
Actually that's not true. Case in point, quantum dots. When the electrons are confined in 3D space that is smaller than the de Broglie wavelength (I.e., nanoscale) the photons (emitted) can ONLY be waves, not particles.
Cheers
Follow Ups:
Not following you. Yes photons at emitted. AFAIK these photons are exhibit the photoelectric effect as well as all the wave effects of light. This was the original effect that required a suggestion of quantization or a sort of particle nature to light. I would be glad to examine evidence to the contrary.
Once electrons are confined to spaces with dimensions below the DeBroglie wavelength the emitted photons cannot act as particles, only as waves. Ref Quantum Confinement. Same idea applies to the ubiquitous CD laser. Ref Quantum Well. That's why the photons from the CD laser form a beam of coherent light. Ref Coherent Light.
Well I know about quantum confinement and coherent light. This light exhibits quantization into photons which is the "particle" part of its quantum nature, just like any other light. When you state these cannot act as particles, you are incorrect. When they interact with a photo detector, they act like discrete particles. If you have evidence to the contrary, I would be glad to examine it.
I actually disagree that the photodector detects photons as particles. A photodetector detects energy. it doesn't count the particles, if that's what you were thinking. In this case specifically electromagnetic energy. The "energy" of the laser is actually specified as 5 mW or whatever. If the power of the light falls below a pre-determined level the light fails to be detected, thus attempting to prevent reflected stray light from affecting results. Besides both quantum dots and CD lasers emit coherent light and coherence is a property of waves, not particles, no?
Edits: 10/08/15
Certainly coherence is a wave phenomena. Light certainly acts as a wave and was long visualized as a purely wave phenomena.
The interaction of light with photosensitive metals led to a puzzle, the photoelectric effect (see link). The eventual explanation was that light, previously considered a wave, exhibited a quantized particulate nature, each particle being labelled a photon.
This was the very beginning of quantum theory. Which has been extensively tested and verified in the century since. There is nothing peculiar to lasers or quantum dots that changes this picture of the light they generate. In fact, you can read references to photon generation in many quantum dot papers.
Well, anyway, you can have the last word on this, I fear that if we do not have an agreement at this point, we never will. See you on a more populated forum like film.
The photoelectric effect has to do with the emission of electrons from a metal surface due to application of light to the surface. Quantum dots and laser emit photons due to the stimulation of electrons by external light or other energy. In the case of the quantum dot the (artificial) atoms actually do not contain nuclei only an empty hole. It is because the quantum dot is nanoscale on the order of the Bohr radius or smaller that the emitted light is wave onlly.
In the case of the audio signal as an electromagnetic wave, like any electromagnetic wave, the wave comprises photons, just not photons in the visible light spectrum. Now are they particles AND waves? You decide.Nice chatting with you.
Edits: 10/09/15
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