Post by: Nicholas Lee on 24/04/2016 21:39:18
Is this eV level known in glass, liquid, and transparent plastics, for electrons to transmission light.
Physicists say that "In most solid or liquid substances, the electron structure is so complex that emissions are not confined to one wavelength, but are smeared out.
Therefore, emission features of solids and liquids are barely discernible."
So basically its like its physicists are saying its to hard to try, because the material maybe has so many different elements, so you cannot find the absorption band of a certain color of light.
But what about a material composed of one atomic element, not mixed with any others.
Could it then be possible to find the absorption, and emission spectrum of the solid material.
The answer to this question is not on the internet.
I am grateful for your help, anything helps, even a few words. :D
Post by: alancalverd on 24/04/2016 23:28:08
I have used the temperature rise caused by the absorption of visible light in carbon to determine the power of a photon beam. It's the best way of measuring laser output power, and with a bit of cunning you can measure the effect of switching on a room light.
Post by: evan_au on 25/04/2016 00:29:45
Quote from: Timemachine2
a solid four inch cubed block of material like black carbonCarbon is used as a practical example of a "black body", since it absorbs all wavelengths of visible and infra-red light very well (and emits them all equally well). It also absorbs radio waves very well. https://en.wikipedia.org/wiki/Black-body_radiation
So you would not select carbon as the material of choice for a "transparent body".
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Can the wavelength, and frequency of any EM wave be increased, or decreased, as the waves pass through a solid four inch cubed blockAs I understand it, the frequency can't be changed, but the wavelength can, when passing through a "linear" transparent optical material like glass, or your eyeball. This is how glasses and your eyeball can focus light.
The amount the wavelength is compressed is determined by the index of refraction of the material. See a list here: https://en.wikipedia.org/wiki/List_of_refractive_indices
There is another way that both wavelength and frequency can be changed, in a "nonlinear" optical material. Green laser pointers work this way: two infra-red photons are turned into one green photon at twice the frequency.
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Could it be done, basically to make the (material) translucent by 2%, even temporarily?This is what happens in a pulsed laser - a high optical power is injected into the material at one wavelength, where the material usually absorbs.
This boosts the electrons into a higher "metastable" state; when most of the electrons are in this higher state, the material becomes more transparent at the wavelength where it was previously opaque.
There are some other odd effects that can be achieved by priming material with a carefully-timed pulse of light, such as "slow light (https://en.wikipedia.org/wiki/Slow_light)": the speed of light at a different wavelength can be slowed to a walking pace, or even stopped.
These effects tend to occur with specific wavelengths, so they are not useful for transmitting color images. If you want to transmit a color image, try a liquid crystal panel, or electro-optical crystals.
Post by: McQueen on 25/04/2016 06:58:50
As I understand it, the frequency can't be changed, but the wavelength can, when passing through a "linear" transparent optical material like glass, or your eyeball. This is how glasses and your eyeball can focus light.This is really quite mystifying because IF the speed of light slows down when moving through a medium AND the frequency remains the same, then the wave-length should decrease not increase:
Suppose the speed of light in a vacuum is 3 * 10 8 metres.
The frequency
of the light is 500 * 10 14 Hz.Then the wavelength
Suppose while travelling through a medium the speed of light is reduced to 2.5 * 108 metres
The frequency
remains the same at 500 * 10 14 Hz.Then the wavelength
Thus the conclusion that the frequency of light remains unchanged while its wave length increases with its passage through a medium is wrong it has to be wrong! On the other hand IF the frequency of the light remains unchanged upon its exit from the medium, it means that the speed of light has slowed due to the process of emission and absorption, without in anyway affecting its frequency or wavelength.
Post by: Colin2B on 25/04/2016 10:22:16
Not mystifying at all, Evan didn't say the wavelength increased.As I understand it, the frequency can't be changed, but the wavelength can, when passing through a "linear" transparent optical material like glass, or your eyeball. This is how glasses and your eyeball can focus light.This is really quite mystifying because IF the speed of light slows down when moving through a medium AND the frequency remains the same, then the wave-length should decrease not increase:
The amount the wavelength is compressed is determined by the index of refraction of the material.
Post by: evan_au on 25/04/2016 11:21:21
Quote from: McQueen
the conclusion that the frequency of light remains unchanged while its wave length increases with its passage through a medium is wrong
I think you are referring to the following sentence:
The amount the wavelength is compressed is determined by the index of refraction of the material.
By saying that the wavelength is "compressed", I tried to imply that the wavelength is shorter when light is travelling through a material of higher index of refraction.
This agrees with the numerical example provided.
(overlap with Colin2B...)
Post by: McQueen on 25/04/2016 13:42:12
The amount the wavelength is compressed is determined by the index of refraction of the material.
By saying that the wavelength is "compressed", I tried to imply that the wavelength is shorter when light is travelling through a material of higher index of refraction.
This agrees with the numerical example provided.
(overlap with Colin2B...)
Sorry to sound contentious BUT if you are speaking in terms of electromagnetic radiation travelling through a medium, then surely if the wave-length is compressed, the light that entered the medium won't be the light that comes out, different wavelength, different frequency. This is the point I was trying to make, namely that light in the form of photons may slow through a medium, due to absorption and emission and THEREFORE the wave-length is compressed without affecting frequency, when the light exits the medium the wave length will also increase due to the change in the speed of light. However, in a wave situation this is not possible. If the wavelength changes , the frequency changes. The two are inextricably connected.
Post by: McQueen on 25/04/2016 18:49:12
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If the wavelength changes , the frequency changes. The two are inextricably connected.
This appears to be true only if the velocity remains constant, it is possible for either frequency or wavelength to change while the other remains constant. In most instances, it is frequency that remains constant while the wavelength undergoes change. The frequency of a sound depends on its source and does not change, the wavelength does.
Post by: evan_au on 26/04/2016 22:53:10
Quote from: McQueen
Sorry to sound contentious BUT if you are speaking in terms of electromagnetic radiation travelling through a medium, then surely if the wave-length is compressed, the light that entered the medium won't be the light that comes out, different wavelength, different frequency.There appears to be a misunderstanding here.
Light that enters a denser material (eg Flint glass, refractive index 1.61) is slowed down by a factor of 1.61, and it's wavelength is compressed by the same factor of 1.61, while its frequency remains constant.
Light that exits the flint glass has its velocity increase by the same factor of 1.61, and its speed increase by 1.61; same frequency, same wavelength, same velocity as light that entered. ie the light which exits is identical to the light that entered the glass (although perhaps now with a slightly different direction, due to diffraction).
This is why the color of objects does not change when you put on your (untinted) glasses.
So the equation v=nλ applies in air, and in the flint glass.
v: velocity
n: frequency
λ:wavelength
As does conservation of energy, by the equation E=ħn
E: Energy of a photon
ħ: Plank constant
n: Frequency
See this link, but be careful about when they are talking about light in a vacuum, or light in a medium: https://en.wikipedia.org/wiki/Photon_energy#Formula
See: https://en.wikipedia.org/wiki/List_of_refractive_indices#List
Post by: Nicholas Lee on 27/04/2016 00:26:47
Question 1. If you mixed any invisible EM waves, like X-rays , gamma waves, ultraviolet waves ,and micro waves with radio waves, and sent the invisible EM waves in microscopic bundles with the original radio wave beam.
So basically the EM waves are intertwined into a single beam, the the beams that absorb are in microscopic bundles, they could be sent even into the carbon cubed four inch block of matter in millisecond timed bursts.
The temperature of the block could be cooled, or even heated up to help with photons either not being absorbed, or help being absorbed.
So any invisible EM waves that do get absorbed by electrons, in ANY wavelength, or ANY frequency could the EM waves not get absorbed by the electrons, or would the electrons just it the surface of the carbon block, and always get absorbed, no matter what wavelength, or frequency, or the small amount of photons you sent to the block, mixed in with radio waves.
Question 2.
Also can the wavelength of any EM waves that DO get absorbed by electrons, can the wavelength be adjusted as the invisible EM waves are already inside the carbon block, if they do not get absorbed on the surface instantly.
Remember the temperature of the carbon block is a factor in absorption, whether the block is heated, up or cooled down.
Thank you for your help, anything helps even a few words
Post by: Atomic-S on 27/04/2016 08:30:46
Post by: Colin2B on 27/04/2016 08:38:30
If you mixed any invisible EM waves, like X-rays , gamma waves, ultraviolet waves ,and micro waves with radio waves, and sent the invisible EM waves in microscopic bundles with the original radio wave beam.If you send out a mix of em waves of different frequencies they don't mix in this way but remain separate. This also happens (or rather doesn't happen) with sound waves otherwise you wouldn't be able to hear separate instruments in music.
So basically the EM waves are intertwined into a single beam, the the beams that absorb are in microscopic bundles, they could be sent even into the carbon cubed four inch block of matter in millisecond timed bursts.
Post by: evan_au on 27/04/2016 11:03:26
Post by: McQueen on 27/04/2016 13:09:41
There appears to be a misunderstanding here.
Light that enters a denser material (eg Flint glass, refractive index 1.61) is slowed down by a factor of 1.61, and it's wavelength is compressed by the same factor of 1.61, while its frequency remains constant.
Point taken, energy is conserved in the form of frequency, while wave-length and velocity may change as light enters a medium. That is the wave point of view and it is valid, however, the photon point of view is also valid. Light slows down and the direction of the light undergoes change. The wave explanation of this bending is particularly beautiful since it is attributed to the leading edge of the wave entering the medium first and travelling a shorter distance, followed by the rest of the wave taking a longer route hence the bending or refraction of light. The photon point of view which is that light slows due to emission and absorption claims that when light slows its direction naturally undergoes change. The photon point of view might carry more weight because scientific experiment has shown that the material of the medium contains atoms that contain electrons which can absorb photons of those energies.
Post by: Nicholas Lee on 27/04/2016 19:21:15
Can any invisible EM waves that get absorbed by electrons pass through solid matter.
Question 1. If you mixed any invisible EM waves, like X-rays , gamma waves, ultraviolet waves ,and micro waves with radio waves, and sent the invisible EM waves in microscopic bundles with the original radio wave beam.
So basically the EM waves are intertwined into a single beam, the the beams that absorb are in microscopic bundles, they could be sent even into the carbon cubed four inch block of matter in millisecond timed bursts.
The temperature of the block could be cooled, or even heated up to help with photons either not being absorbed, or help being absorbed.
So any invisible EM waves that do get absorbed by electrons, in ANY wavelength, or ANY frequency could the EM waves not get absorbed by the electrons, or would the electrons just it the surface of the carbon block, and always get absorbed, no matter what wavelength, or frequency, or the small amount of photons you sent to the block, mixed in with radio waves.
Question 2.
Also can the wavelength of any EM waves that DO get absorbed by electrons, can the wavelength be adjusted as the invisible EM waves are already inside the carbon block, if they do not get absorbed on the surface instantly.
Remember the temperature of the carbon block is a factor in absorption, whether the block is heated, up or cooled down.
Thank you for your help, anything helps even a few words.
Post by: evan_au on 27/04/2016 22:41:06
Quote from: McQueen
The photon point of view which is that light slows due to emission and absorptionCarbon (graphite), with its many connected atoms in many structures has a wide conduction band, and absorbs photons over a very wide range of frequencies.
In contrast, glass is a non-conductor, and does not have the same broadening of energy levels in its electron orbitals. The atoms and molecules of pure glass do not have energy levels which absorb and re-emit real photons in the visible range. That's why it is transparent.
I can't comment on virtual photons...
https://en.wikipedia.org/wiki/Transparency_and_translucency#Introduction
Post by: Nicholas Lee on 28/04/2016 04:01:51
.... transparent plastics for light to transmission completely through the material.
Is this eV level known in glass, liquid, and transparent plastics, for electrons to transmission light.
Physicists say that "In most solid or liquid substances, the electron structure is so complex that emissions are not confined to one wavelength, but are smeared out.
Therefore, emission features of solids and liquids are barely discernible."
So basically its like its physicists are saying its to hard to try, because the material maybe has so many different elements, so you cannot find the absorption band of a certain color of light.
But what about a material composed of one atomic element, not mixed with any others.
Could it then be possible to find the absorption, and emission spectrum of the solid material.
I am grateful for your help, anything helps, even a few words. :D
Post by: McQueen on 28/04/2016 09:24:02
Quote from: McQueenThe photon point of view which is that light slows due to emission and absorptionCarbon (graphite), with its many connected atoms in many structures has a wide conduction band, and absorbs photons over a very wide range of frequencies.
In contrast, glass is a non-conductor, and does not have the same broadening of energy levels in its electron orbitals. The atoms and molecules of pure glass do not have energy levels which absorb and re-emit real photons in the visible range. That's why it is transparent.
I can't comment on virtual photons...
https://en.wikipedia.org/wiki/Transparency_and_translucency#Introduction
Stop your gloating, with your derisive reference to 'virtual photons' ! What happens when a quoted source (a) contradicts itself (b) has experimental proof that what the source say can't happen does in fact happen ? Do you apologise or just go ahead with your gloating safe in the belief that the majority view supports you ?
Look at the following article quote:
"As an extreme example of light "slowing" in matter, two independent teams of physicists claimed to bring light to a "complete standstill" by passing it through a Bose–Einstein condensate of the element rubidium, one team at Harvard University and the Rowland Institute for Science in Cambridge, Mass., and the other at the Harvard–Smithsonian Center for Astrophysics, also in Cambridge. However, the popular description of light being "stopped" in these experiments refers only to light being stored in the excited states of atoms, then re-emitted at an arbitrarily later time, as stimulated by a second laser pulse. During the time it had "stopped," it had ceased to be light. This type of behaviour is generally microscopically true of all transparent media which "slow" the speed of light. "
https://en.wikipedia.org/wiki/Speed_of_light
And of course if you consider it from this point of view the idea that light in the form of photons can breeze through a material without interacting in any way with the material and still be slowed down is ridiculous. Further if light is slowed energy is involved, if energy is involved then photons not waves are involved. Because at the level of atomic structure it is all individual interactions, between photons and electrons.
Post by: evan_au on 28/04/2016 11:38:28
Quote from: McQueen
derisive reference to 'virtual photons'I'm sorry if my reference to virtual photons offends you. Some people take virtual photons very seriously, in the context of light propagating through media.
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if light is slowed energy is involved, if energy is involved then photons not waves are involved.I agree that light carries energy, just as ocean, gravitational and radio oscillations do.
I agree that photons of visible light, gamma rays and radio can carry energy (and gravitons too, if they exist).
Please clarify why light waves, ocean waves, gravitational waves and radio waves cannot carry energy.
Especially since ocean waves can change speed (in shallower water) and coherent laser light waves can change speed (in glass). I have also heard it said that gravitational waves slow down in areas with non-zero density of matter, which is apparently a prerequisite for our gravitational wave detectors to function.
Post by: evan_au on 28/04/2016 12:50:19
Quote from: Timemachine2
Can EM waves like radio waves that can traverse solid matter, be combined/mixed with other EM waves to become EM waves that get absorbed by electrons?
Perhaps there is some confusion here over what it means to combine or mix electromagnetic waves?
Most materials are quite "linear" in their optical properties.
If you put in 3 waves of different frequencies, they behave quite independently (as if the other wave was not present).
* If the material is transparent to all 3, then all 3 will come out the other side unchanged.
* If the material is opaque to all 3, then all 3 will raise the temperature of the material.
* If the material is reflective to all 3, then all 3 will be reflected.
* If the material is dispersive, then all 3 will come out at slightly different angles.
* And it is quite possible to have mixtures of the above behaviors, for example one frequency may be reflected, and another frequency transparent (eg silicon has a metallic lustre at visible frequencies, but is transparent to infra-red).
If you have EM radiation with widely varying frequencies (eg "X-rays , gamma waves, ultraviolet waves ,and micro waves with radio waves"), they are almost certain to have widely varying responses. After all, the visible spectrum only spans a factor of 2 in frequency, and yet we see dispersive differences in a rainbow.
Some optical materials are non-linear (https://en.wikipedia.org/wiki/Nonlinear_optics):
It is quite possible to put in 3 frequencies, and get out 6 or more frequencies!
The behavior at these other frequencies may be quite different from the behavior at the frequencies that are input.
If you want to make something transparent, I suggest:
* Avoid graphite; it turns a wide variety of EM frequencies into heat.
* On the other hand, the same element in a different crystalline form (diamond) is transparent to visible frequencies.
* Select a frequency where the material is already fairly transparent
* Unfortunately, if it is perfectly transparent, you will find out nothing about the interior of the material!
I get the impression that you are interested in studying biological samples
* Infra-red penetrates the body better than visible light
* radio waves can penetrate the body fairly well; MRI machines can take internal images with reasonable resolution.
* X-Rays can also penetrate the body very well (except bone). CT machines can take high-resolution images, even through the skull
* There has been a lot of progress recently in imaging biological systems using dyes that fluoresce in different colors
* Some of these can be activated when certain genetic pathways are activated, allowing the study of functioning cells.
* You also need to be careful about damaging the test subject - X-Rays are ionizing radiation, and genetic engineering to insert fluorescent proteins might induce cancer. Peeking deep inside the brain with optical fibers will cause injury.
Post by: McQueen on 28/04/2016 14:45:04
I'm sorry if my reference to virtual photons offends you. Some people take virtual photons very seriously, in the context of light propagating through media.
Sorry , my bad, I was out of line to make such a statement. Incidentally I do believe that 'virtual photons' exist and play an indispensable part in the working of the world and the Universe. P.S. On re-reading my post I realise that it is even worse than I had originally thought. Once again my apologies.
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Please clarify why light waves, ocean waves, gravitational waves and radio waves cannot carry energy.
Out of these "waves" only ocean waves are true waves that disperse their energy across the wave front i.e., the energy is shared in common, all of the others ( leaving aside gravitational waves) have discrete energies as demonstrated by Max Planck..
Coming back to the topic of light slowing down as it travels through glass..... Here is another quantum mechanics explanation that also involves absorption and emission of photons by electrons as they travel through glass:
"To make the classical picture quantum, we say that a single photon entering the material will potentially be absorbed and re-emitted by each of the atoms making up the first layer of the material. Since we cannot directly measure which atom did the absorbing, though, we treat the situation mathematically as a superposition of all the possible outcomes, namely, each of the atoms absorbing then re-emitting the photon. Then, when we come to the next layer of the material, we first need to add up all the wave-functions corresponding to all the possible absorptions and re-emissions.
Thus, we more or less reproduce the Huygens’s Principle case, and we find that just as in the classical case, the pieces of the photon wave-function corresponding to each of the different emissions will interfere with one another. This interference will be constructive in the forward direction, and destructive in all the other directions. So, the photon will effectively continue on in the direction it was originally headed. Then we repeat the process for the next layer of atoms in the medium, and so forth.
It’s important to note that when this picture is valid the probability of being absorbed then re-emitted by any individual atom is pretty tiny– when the light frequency is close to a resonance in the material, you would need to do something very different. (But then, if the light was close to a resonant frequency of the material, it wouldn’t be a transparent material…) while the probability of absorption and re-emission is tiny for any individual atom, though, there are vast numbers of atoms in a typical solid, so the odds are that the photon will be absorbed and re-emitted at some point during the passage through the glass are very good. Thus, on average, the photon will be delayed relative to one that passes through an equal length of vacuum, and that gives us the slowing effect that we see for light moving through glass."
Post by: Nicholas Lee on 29/04/2016 18:06:23
Post by: evan_au on 30/04/2016 23:58:04