# Does light speed apply to all waves traveling in vacuum?

by Crazy Tosser
Tags: apply, light, speed, traveling, vacuum, waves
 P: 175 Seriosly, waves have different frequencies, and light is somewhere in the middle of the EM spectrum, then maybe the right or left side could travel faster than c
 P: 277 Light is generally the term used to refer to electromagnetc waves in the visual spectrum (but its really the same as other E&M waves, just at different energies). They all behave generally the same, i.e. all E&M waves travel at the speed of light.
 P: 87 All massless waves (and all massless particles) travel at the speed of light.
 PF Gold P: 8,964 Does light speed apply to all waves traveling in vacuum? That includes gravity, by the way. I think that in one regard, you can say that not all waves travel at c in vacuum, but I'm not sure if my reasoning applies. It seems to me that the matter waves associated with a particle can't do so, since the particle itself can't.
P: 816
CT, all EM waves travel at the same speed in a vacuum. As far as I am aware this is not the case when dealing with a medium in which the waves are travelling slower.

 Quote by Phlogistonian All massless waves (and all massless particles) travel at the speed of light.
If by speed of light you mean around $3\times10^8$ then I can't see how that is correct.
P: 249
 Quote by Crazy Tosser Seriosly, waves have different frequencies, and light is somewhere in the middle of the EM spectrum, then maybe the right or left side could travel faster than c
The phase velocity of a wave is a product of the frequency and wavelength:

L*f=v

The electromagnetic wave equation has solutions with different frequences, but the wavelength must be inversely proportional to the frequency, so the product is always the same:

L*f=c
P: 422
 Quote by Danger That includes gravity, by the way. I think that in one regard, you can say that not all waves travel at c in vacuum, but I'm not sure if my reasoning applies. It seems to me that the matter waves associated with a particle can't do so, since the particle itself can't.

Has it been experimentally proven that gravity waves travel at the speed of light.
P: 87
 Quote by _Mayday_ If by speed of light you mean around $3\times10^8$ then I can't see how that is correct.
The original question was about waves in a vacuum.
P: 816
 Quote by Phlogistonian The original question was about waves in a vacuum.
That doesn't make what you said correct.
P: 87
 Quote by _Mayday_ That doesn't make what you said correct.
You can think what you want. I won't engage in a pointless argument over semantics.
 P: 175 Well, how about traveling slower than the speed of light? If you are in a car that's goin at 100mph and you light a flashlight backwards, does the light travel at c-(100mph)?
Emeritus
PF Gold
P: 29,243
 Quote by Crazy Tosser Well, how about traveling slower than the speed of light? If you are in a car that's goin at 100mph and you light a flashlight backwards, does the light travel at c-(100mph)?

http://hyperphysics.phy-astr.gsu.edu...iv/einvel.html

The speed of light is constant in all inertial frames, no matter the speed of the source.

Zz.
P: 2,251
 Quote by bassplayer142 Has it been experimentally proven that gravity waves travel at the speed of light.
only to within 20%, IIRC.
P: 286
 Quote by Crazy Tosser Well, how about traveling slower than the speed of light? If you are in a car that's goin at 100mph and you light a flashlight backwards, does the light travel at c-(100mph)?
Excellent question, CT, and the answer is very important (ZapperZ already mentioned it). Make sure to keep reading every text you can get your hands on, because we've all asked this question at one time or another; if you can accept the true answer it will blow your mind.

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