Why is light not affected by magnetic fields?

[Little Bang]

So if we pass a beam of light through a moving magnetic field experiment has shown that the light is not polarized?

[CraigD]

Originally Posted by Little Bang

Since EMR has both electric and magnetic components how do we know that a magnet field doesn't cause something like rotation of the wave?

We know that if a medium containing electrons (eg: glass or interstellar gas) is subjected to a magnetic field, polarized light that interacts with that medium (ie: passes through it) has its plane of polarization rotated. This is the Faraday effect. It depends on the wavelength of the light, the density and molecular structure of the medium, and the orientation and strength, but not the direction, of the magnetic field. Different materials can rotate the plane in a positive or negative direction, and if the magnetic field is oriented perpendicular to the light beam, zero rotation occurs.

According to theory, as the density of electrons in the medium is reduced, so is the rotation. Visible light in one of the most effective Faraday rotator mediums, terbium gallium garnet, has a Verdet constant of -40 rad/T/m, glass around 1.8e-7, typical interstellar gas about 2e-20. (from data and links from the preceding wikipedia link, and some simple calculations)

Originally Posted by Little Bang

If there have been experiments that confirm magnetic fields have no effect what so ever on light please point them out.

This “proving a negative” would be pretty tough. The best experiments can show, I think, is that as a medium approaches a perfect vacuum, its Verdet constant approaches zero. To measure a Verdet constant of absolute zero, you’d need to have a vacuum better than found in deep space stretching for many light years and subjected to a strong magnetic field, and even then, you’d not be sure that your experiment was not sufficiently sensitive to detect some tiny effect not predicted by theory.

Most measurements of very small Verdet constants (usually called “rotation measure”, and with an additional unit to allow multiplication of the square of the light’s wavelength) are made in combination with other measurements to determine the density of matter in interstellar space. Given that theory predicts a zero Verdet constant for absolute vacuum, and all experimental data supports it, I doubt many experimental resources will be spent attempting to support the theory greater certainty.

Originally Posted by Little Bang

So if we pass a beam of light through a moving magnetic field experiment has shown that the light is not polarized?

It’s important to note that the Faraday effect doesn’t itself polarize light, but rotates the plane of polarization of previously polarized light. Un-polarized (randomly polarized) light will still be randomly polarized after its many planes are rotated by the Faraday effect.

The Faraday effect doesn’t require a changing/moving magnetic field. Change in the strength and orientation of the field is averaged to determine the total rotation of the material.

[Jonthegreat]

After reading up on the [I]extensive[I] information posted specifically on a design for a 'light accelerator' that was plaguing my head, I have a question.

Understanding that light waves cannot be affected by EM or EMR (as photons have neither charge nor resting mass) and that fields cannot be 'bent' by other fields I have arrived at my next proposal.

What about the field interference on an oscillating, polarized, and accelerated fashion with staggered strengths of interference? Would, in effect, the field itself be accelerated?

As light travels through such an accelerated field, is it possible to accelerate such motion beyond the constants of light?

Perhaps I am grasping at straws here...

PS... This is not referring to the above rotating situation, rather linear acceleration. Also the medium would be of the gaseous type. The threads I was attempting to comment on also seemed to disappear after posting. This is more under the umbrella, DOES light bend under the effects of magnetism.

[logy]

Originally Posted by Jonthegreat

After reading up on the [I]extensive[I] information posted specifically on a design for a 'light accelerator' that was plaguing my head, I have a question.

Understanding that light waves cannot be affected by EM or EMR (as photons have neither charge nor resting mass) and that fields cannot be 'bent' by other fields I have arrived at my next proposal.

What about the field interference on an oscillating, polarized, and accelerated fashion with staggered strengths of interference? Would, in effect, the field itself be accelerated?

As light travels through such an accelerated field, is it possible to accelerate such motion beyond the constants of light?

Perhaps I am grasping at straws here...

PS... This is not referring to the above rotating situation, rather linear acceleration. Also the medium would be of the gaseous type. The threads I was attempting to comment on also seemed to disappear after posting. This is more under the umbrella, DOES light bend under the effects of magnetism.

According to Einstein, the speed of light in vacuum is constant and never changes. If anyone where to discover an experiment that demonstrates otherwise, the theory of relativity will fall apart. BUT that does not mean that you can't get light move slower, or for something to like it's moving faster then the speed of light. if you shine a light through a transparent material (say glass) it will look like it's traveling at a slower speed, but that is only because the light photons are absorbed and then re-emitted by the glass. the phtons of light coming out of the glass are not the same ones that entered the glass. According to wikipedia scientists have managed to completely halt light boze-einstein condensate. I don't fully understand that phenomenon but I think that it is quite amazing !!! .

If you wish to make something move faster then the speed of light using interference patterns, I don't see why it won't work. And I will elaborate;
Let’s say that Johnny has a strong laser torch and he is pointing it on a very distant object. On that object, you will get a dot of light from the laser beam. now if Johnny where to move the laser torch fast enough, that dot will move faster then the speed of light, since the laser only has to move a couple centimeters in order for the dot to move thousands of meters. but for both dots to be illuminated it will require for the light to travel from the laser to the distant planet. The light can reach the second dot within a tiny fraction of a second (say 1/300,000,000 of a second, approximately the time it takes light to travel one meter) of reaching the first dot, and the dots can be thousands of meters away from each other.

The key thing to note is that nothing actually moves from dot A to dot B, rather, light is moving from the laser to both dots. And I see no reason that this cannot be done with interference patterns so that within an area that is illuminated by lasers, you will have a dark spot (due to interference) that 'moves' faster then the speed of light.

[Jonthegreat]

Okay. Fair enough. Back to the situation of alternating field interference - can a wavelength be.. 'accelerated'.. to a wavelength of higher intensity without changing the output of the source, such as a beam from a laser? My thoughts, to put it simply, are to construct a resonance device that compounds so that a weak wavelength (such as radio &/or laser pointer) would end up an intense wave out the other end. I understand E's determination that light is as fast as light can go. Thank you for reminding me.

This may seem pointless, however, due to the fact that the energy required to do so may far exceed both the source and the product combined. The thoughts are of using such resonance to harness such energies found in nature *ie Sun*

Am I a hopeless dreamer? or could there be light at the end of the tunnel, no pun intended.

I am somewhat familiar with how photovoltaic cells work -- this is unrelated. More of a refocusing/amplification of a weak source to a strong product.

If this sounds unfocused or inconclusive I guess sum me up as asking "What if?"

: ( Could be the 101.2F fever I got going on too...

[logy]

Originally Posted by Jonthegreat

Okay. Fair enough. Back to the situation of alternating field interference - can a wavelength be.. 'accelerated'.. to a wavelength of higher intensity without changing the output of the source, such as a beam from a laser? My thoughts, to put it simply, are to construct a resonance device using placed induction of current producing EMR so that a weak wavelength (such as radio &/or laser pointer) would end up an intense wave out the other end.

This may seem pointless, however, due to the fact that the energy required to do so may far exceed both the source and the product combined. The thoughts are of using such resonance to harness such energies found in nature *ie Sun*

Am I a hopeless dreamer? or could there be light at the end of the tunnel, no pun intended.

I am somewhat familiar with how photovoltaic cells work -- this is unrelated. More of a refocusing/amplification of a weak source to a strong product.

Jonthegreat, I don’t think that you’re not a hopeless dreamer, far from it. In fact your ideas are in the cutting edge of scientific research in more the one area !

First of all, intensity in this context usually refers to the amount of energy produced by a specific light source, i.e. the number of photons, which cannot be changed without 'creating' more photons.

In regards to changing the amount of energy per photon, that would mean changing it's wave length, and that happens all the time. one example is Red shift in astronomy which is a result of the Doppler effect.

an example that is closer to what you motioned is lazer cooling , where essentially they use laser beans that have slightly less energy then what is required in order to excite an atom. since heat is essentially movement (or 'vibration' in solids) of atoms, if the atom is moving *towards* the light , then the light will appear to have a higher frequency from the atoms perspective and will be absorbed, slowing down the atom by 'taking' kinetic energy and momentum from it. Then, it will be re-emitted in a random direction with a slightly higher average frequency.

If you where to build a machine that generates EMR, it will emit photons all on it's own, which if i understand correctly, is how radio's and mobile phones work. So your idea is being used by billions of people already !

In regards to harnessing energy from the sun, it depends, if you are talking about sunlight, that's what solar panels do, convert the light energy into electrical energy.
since you cannot create energy from nothing, the sun itself has to get its energy from somewhere and that comes from nuclear fusion , something that scientists have been trying to duplicate for decades, but are having trouble containing the hydrogen because fusion requires very high temperatures, in excess of 100 million degrees Kelvin, while any known material will vaporize before it reaches 10,000 degrees.

[Little Bang]

Jon, haven't you figured out yet that no one on this planet can explain electromagnetic radiation? Just like gravity and charge they give their interpretation of theory. But 99% of the scientific community will agree with them.

[Jonthegreat]

That's about as satisfying as NOT dying while driving today.

I enjoy playing with ideas that people simply accept because there have not been found any reasons why it IS NOT true. Gravity is a big one. The concept of the "speed of light" is another one.

Perhaps a drawing is in order for my question. I see proper answers but none are as satisfying as what I am looking for.

I appreciate the responses!!! If I HAPPEN to come across anything landmark in my design, I'll be referencing this site as a haven for people who have questions!!

[gregdevid]

Originally Posted by logy

Moderation note: the first 5 post of this thread were moved from [Q] Light and magnets , because they are more of an in-depth discussion of physics than a simple question & answer

in my humble oppinion:

light is not affected by magneting or static electrical fields because it has no mass and it's speed is constant !
magnets and static electricity creat a force field which can accelerate objects that have mass and gain gain or loose kinetic energy and momentum, like say other magnets or an electrically chared charged piece of metal, but light itself travels at the speed of light, had no "rest mass" which means no mass for the purpose of this discussion and therefore will travel in a streight line unless one of the following happens.
1.it hits a reflecting or refracting surface
2. it enters a gravitational field, in which case, the curve in space itself will make it "curve".

simply put, since light had no mass and cannot be accelerated (as acceleration shanges speed), it will not react to a force.

hi,

EM fields bend the path of moving particles such as in the Solar Wind, or simply in a TV tube which uses EM fields to deflect (bend) electron paths.
Since light is both a wave and a particle at the same time, you might think that this would cause light to be bent if only you had a strong enough field.

[CraigD]

Originally Posted by gregdevid

EM fields bend the path of moving particles such as in the Solar Wind, or simply in a TV tube which uses EM fields to deflect (bend) electron paths.
Since light is both a wave and a particle at the same time, you might think that this would cause light to be bent if only you had a strong enough field.

Solar wind particles (mostly protons and electrons) and electrons are charged particles. Photons, however, have zero charge. Thus electrodynamics, either the Classical electromagnetism developed in the 19th century or the Quantum electrodynamics (QED) developed in the 20th, predicts that regardless of its strength, light won’t be bent by a magnetic field.

QED gives us another way of looking at it. Magnetic force, the interaction that defines magnetic fields, is composed of photons. Because they follow Bose-Einstein statistics, photons don’t interact in a momentum-effecting way. So photons can’t be affected by magnetic fields.