Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: sorincosofret on 19/05/2008 00:39:04
-
Angular momentum for light and electromagnetic waves
Background and actual explanation
The energy of a photon is directly related to its frequency E=hν and the momentum of a photon is equivalent to the energy divided by the speed of light p = E/c . Photons with different energies carry a different momentum
Besides their momentum, any photon has another characteristic - spin angular momentum which is independent of its frequency.
Spin angular momentum is essentially circular polarization for a photon and has only two possible values: ±h/2π. In an intuitive representation, because this is a quantum characteristic without classical correspondent, the angular momentum is the helical momentum of the photon along its flight path.
The experimental proof that a fascicle of polarized light carries an angular momentum was proved by Beth in 1936.
The circular polarised light passing through a sheet of material change its polarisation and consequently the sheet is rotated with a small angle. In order to amplify the microscopic effect the change of polarisation due to light reflection on a second silvered material sheet is used as in fig.1. The sheets are suspended and have the possibility of rotation.
When incident light, left polarised pass through sheet L, changes its polarisation and become right polarised. Light passes two times through the second sheet l and due to the change of polarization during reflection, arrive again at sheet L with polarisation changed related to initial incident light. In this way, passing two times through the sheet L, the effects are added and become more accessible to be measured.
[ Invalid Attachment ]
Figure 1. Beth simplified device
If there are emitted N photons which pass once through sheet, there will be an angular momentum transferred to sheet equal with:
M = N*h/2π
Proposed further experiment
A repetition of Beth experiment with microwaves instead of light can differentiate between comportment of light and an electromagnetic wave.
According to actual quantum theory, a microwave photon carries the same amount of angular momentum like a light photon.
Consequently when a microwave source with the same power is used instead of light and of course the sheets of materials are changed with a material transparent for microwave, the same effects should be obtained.
The L sheet must be made from a high transparent microwave material already available on the market as example polypyrrole films or microtubules of polyaniline. L sheet can be made sticking two films of polypyrolle, one transparent for microwave and a secondary doped film, having high reflectivity capacity for microwave; this second film is practically the silvered mirror from the light case experiment.
In reality, using a microwave source and adapted layers, the result is completely negative and the sheets are not rotating.
The fundamental difference between a wave and a corpuscle regards the possibility to carry an angular momentum. Light photons (from IR to gamma) having a corpuscular nature can carry a small angular momentum.
Electromagnetic waves do not carry an angular momentum and independent on the rotation of electric or magnetic component of wave, an electron does not have enough time to react at this changes.
Let’s consider that electromagnetic waves hit an electron, in the first semi period, when the electric field E increases, as in fig. 2. In this case the electron will be attracted toward the direction of increasing electric field.
[ Invalid Attachment ]
After a semi period, the electric field changes its direction, and of course the electron changes its direction of motion, too, like in fig. 3.
[ Invalid Attachment ]
Because the change of electric field direction is made more then 108 times per second the electron due to its inertia does not move at all.
Consequently an electromagnetic wave can’t produce a macroscopic angular momentum at absorption or reflection.
The detailed interaction between electromagnetic waves and matter will be described in further study.
For the proposed experiment, it is necessary to emphasize that in case of microwaves, the layer of material does not twist.
-
This is dealt with very well in many textbooks. Try reading one.
-
Dear Sophie,
Please indicate me such basic-degree level textbooks where the difference between angular momentum of electromagnetic wave and light is treated.
Up to date, I have read only in the last year about 200 high level books and there is no mention about such difference.
Of course... the experiment is quasi forgotten...
Regards,
-
Perhaps, if angular momentum of em waves has not been treated seriously, the books could actually be right? Or is it another Scientific Conspiracy by the Establishment?
Certainly, your treatment of electrons in em fields is a bit over - simplified and does not even allow for a simple phenomenon like reflection at a metal surface.
Apart from scanning these 200 books for your key words, how much did you understand from them of conventional theory? If you are to dismiss it, you really need to join the enemy and understand what he is saying first.
-
I remind you the fact that this topic was started from your idea that EM waves and lights are the same thing and your GPS and light must follow the same lows.
I gave you some simple examples which contradict this idea and is a piece of cake for a laboratory as Oxford or Cavendish to check this ,,idea". It is not the place and the time to enter into mathematical demonstration, which makes the subject of the corpuscular nature of light book. The comportment of electromagnetic waves and interaction with matter will be part of another book.
There are about 25 years of unpayed and difficult work made in order to arrive at this stage with my theory. I have finished a faculty with double specialisation chemistry and physics, and of course mathematics plays a role of connector between them. Probably, you think that it is the first time when I heard about tensors, Lie algebra, operator, etc, but this is your oppinion. My experience up to date told me that any time when a clear idea is missing scientist try to hide after mathematical formulas.
As you have seen, in any topic posted, I put a first part where the actual description without mathematical description, is provided. If I will put also a complicated and detailed mathematical description, none will read the entire topic. So if you think I made a bad actual interpretation please correct me...
I cite you:,,if angular momentum of em waves has not been treated seriously"...
Why is not treated seriously? You insinuate, that all actual scientific books are only indigo copy of some dusty books without any verification ?
In this case please make a new treatment of electromagnetic waves momentum...
My theory tells there is no electromagnetic wave momentum, and the polarization of electromagnetic waves is a different thing of photon polarization. But in order to understand this fact you must discuss with a radioamateur or through your experiment to see what does it mean these things.
Regards
-
I think you are confused with what the word 'Theory' means to Scientists.
A Theory is an idea which expresses, either verbally or with Maths, a relationship between Scientific quantities. To be worthy of the name it must justify itself with evidence, observation, successful prediction or, possibly a mathematical derivation of a result based on existing and accepted fact. The language used is frequently Maths because it is less liable to misinterpretation.
A Theory is not something which involves a string of well known Science words and elementary facts, loaded with complaints that established Scientists know nothing and have been suppressing the truth for decades. A Theory must commit itself to concrete statements which can be verified. Perhaps you could make some statements which could be tested.
Anything else tends to be 'an interesting idea which we could chat about'.
If one wants to be taken seriously, one must either have a track record or produce a complete piece of work for scrutiny by ones peers.
-
Sophie
I remind you that I've studied for about 30 years the actual theories.
You haven't read nothing about my theories. On my site and on the forums there are some simple and cut/off experiments.
After you will read at least one book related to my theories in a field of physics, please make comments on the subjects. The general discusion: what is and what isn't a theory are not my speciality.
It seems that your nick does not fit at all with your manifestation. I hope you know what does it mean Sophie in Greek.