# The Naked Scientists Forum

### Author Topic: Must electromagnetic waves go through an accelleration phase?  (Read 2459 times)

#### Jared Harding

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##### Must electromagnetic waves go through an accelleration phase?
« on: 02/03/2011 07:30:03 »
Jared Harding asked the Naked Scientists:

Hi Chris,

I was considering the other day in a Physics lesson whether electromagnetic waves have an acceleration phase to attain their velocity upon emission? I have asked the opinions of maths, mechanics and physics teachers and as would be expected Iv'e had varying answers. I have considered myself that the answer must be no (partly because quantum theory seems to always defy logic and simple mathematical logic would argue there must be an acceleration phase); the only explanation I could offer for this was the possibility of a manipulation of space or time such that there is no acceleration phase, as it seems light always manages to manipulate itself in such a manner that it always travels at its constant speed (in the same medium of course). Your outlook would be most appreciated.

Jared Harding.

What do you think?
« Last Edit: 02/03/2011 07:30:03 by _system »

#### syhprum

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##### Must electromagnetic waves go through an accelleration phase?
« Reply #1 on: 02/03/2011 08:00:57 »
I have always understood that there is a phase shift between the electrical and magnetic components of the electromagnetic wave within the first quarter wavelength as they leave the source of radiation

#### Soul Surfer

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##### Must electromagnetic waves go through an accelleration phase?
« Reply #2 on: 02/03/2011 09:57:34 »
No all wave motions are based on the "elasticity" of the substance involved in the wave motion.  In wave motion the potential energy components.  (energy stored in disturbing the medium) and the kinetic energy components (dynamic energy in the motion of the medium) are progressively exchanged as the wave propagates but in general after the wave has passed the medium is unaltered.  So all the acceleration is taking place locally as part of the wave motion itself and unlike a particle accelerating the wave motion does not need to accelerate in the conventional sense.

#### yor_on

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##### Must electromagnetic waves go through an accelleration phase?
« Reply #3 on: 06/03/2011 13:16:44 »
If EM radiation is defined as Electrons, yes they must. If we are talking about the radiation, radiated by those electrons as they excites by getting infused with 'energy'? Nope, don't think so. Radiation are photons.

#### Geezer

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##### Must electromagnetic waves go through an accelleration phase?
« Reply #4 on: 07/03/2011 01:13:38 »
I don't believe it's necessary to assume that photons are not "wavelike" just because they have quantized energy.

If they are "wavelike", there is no need for acceleration because the medium does not have velocity. Also, if any acceleration was required, it would consume an infinite amount of energy, which sounds a bit unlikely.

#### JP

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##### Must electromagnetic waves go through an accelleration phase?
« Reply #5 on: 07/03/2011 04:03:17 »
I don't believe it's necessary to assume that photons are not "wavelike" just because they have quantized energy.

That's the main theme of quantum mechanics.  Particle-like things can also behave in a wavelike manner and wavelike things in a particle-like manner.

#### Geezer

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##### Must electromagnetic waves go through an accelleration phase?
« Reply #6 on: 07/03/2011 04:24:19 »
I don't believe it's necessary to assume that photons are not "wavelike" just because they have quantized energy.

That's the main theme of quantum mechanics.  Particle-like things can also behave in a wavelike manner and wavelike things in a particle-like manner.

I used to find that very frustrating, but now I think it's quite fascinating.

#### yor_on

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##### Must electromagnetic waves go through an accelleration phase?
« Reply #7 on: 07/03/2011 12:46:47 »
Electrons accelerate, photons/waves do not. Give it a 'invariant mass' and you will have an acceleration. Take it away, and you will have no acceleration. We know that photons spontaneously can 'fluctuate into a charged fermion-antifermion pair', so there you might assume a momentarily deceleration if for example created outside a event horizon, splitting up aka 'Hawking radiation'.

As for equalizing matterwaves with photons?
Theoretically it's possible, but matter will always have a acceleration phase if set in motion.
« Last Edit: 07/03/2011 12:48:33 by yor_on »

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##### Must electromagnetic waves go through an accelleration phase?
« Reply #7 on: 07/03/2011 12:46:47 »