Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: flr on 10/10/2013 06:39:26
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We know from Maxwell equations that light can be seen as an electromagnetic wave.
The oscillations of vectors E and B are into directions perpendicular to the direction of wave propagation.
Can it be (theoretically) conceivable to have light as 'longitudinal wave' in which vectors E and B oscillate parallel to the direction of motion?
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We know from Maxwell equations that light can be seen as an electromagnetic wave.
The oscillations of vectors E and B are into directions perpendicular to the direction of wave propagation.
Can it be (theoretically) conceivable to have light as 'longitudinal wave' in which vectors E and B oscillate parallel to the direction of motion?
The transverse nature of E/M waves suggests that the E/M medium (aka aether) is a solid, since fluids cannot transmit transverse waves. I personally believe E/M waves propagate just like acoustic shear waves.
Solids also support longitudinal waves. Without going too deeply into my model, I believe dark energy is a longitudinal wave. It propagates like acoustic pressure waves at a much greater speed than light. Dark energy is not electromagnetic, but it exchanges momentum with E/M waves. That's about all I can say outside the New Theories forum.
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Maxwell's equations (http://en.wikipedia.org/wiki/Electromagnetic_wave_equation#The_origin_of_the_electromagnetic_wave_equation) define the relationship between the electric and magnetic fields, including the direction of the electric field due to a change in the magnetic field, and the direction of the magnetic field due to a change in the electric field.
We are most familiar with plane-polarised light (used in some sunglasses), but there is also circularly-polarised (http://en.wikipedia.org/wiki/Circular_polarization) light (used in some 3D cinemas), where the direction of the electric field rotates over time. Despite the fact that the direction of the electric field rotates over time, the instantaneous direction of the electric field remains at right angles to the magnetic field and the direction of propagation.
Some mantis shrimp are reported to be able to detect circularly-polarised light.
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Can it be (theoretically) conceivable to have light as 'longitudinal wave' in which vectors E and B oscillate parallel to the direction of motion?
The short answer is no. For any EM field, the direction of energy flow, defined through the Poynting vector is always perpendicular to the electric and magnetic fields at any point.
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The short answer is no.
I agree.
For any EM field, the direction of energy flow, defined through the Poynting vector is always perpendicular to the electric and magnetic fields at any point.
I disagree. I think you might have in mind the fact that the radiation produced by an arbitrary finite source has those properties. However that is not the general case. I'm sure that you know that in a wave guide the power flow is along say the z-axis but the fields have non-zero components along that axis. Waveguides for light are fiber optic cables. However even in the case of a waveguide the fields are not parallel to the flow of power/direction of wave propagation.
I long time ago I started working on a webpage to describe all of this. I found it just now and perhaps could finish writing it and put it on my website soon.
This too would make a great FAQ.