Question

Have there been any experiments comparing speeds of X-rays with microwaves?

In other words, has it been determined that speed of electromeagnetic radiation is constant irrespective of the frequency?

Answer 1

Read - http://en.wikipedia.org/wiki/Speed_of_light#Connections_with_electromagnetism

Answer 2

I believe we know that all electromagnetic radiation has the same speed in vacuum.

Answer 3

I was just reading the following in Wikipedia: "Maxwell's equations predicted an infinite number of frequencies of electromagnetic waves, all traveling at the speed of light. This was the first indication of the existence of the entire electromagnetic spectrum."

However, I was wondering if this has been confirmed experimentally! I shall be checking the premise Maxwell was operating on.

Answer 4

I should certainly think so. You would only need to sample the E/M spectrum to find that out.

Answer 5

Right, it would be easy to determine. I am sure there must be actual experiments to that effect now that we can determine such speeds to a good bit of accuracy.

Answer 6

I somehow have an intuitive feeling that the speed should reduce with increasing frequency. This may be most apparent when the speed of gamma rays is compared with the speed of ELF.

Answer 7

I would suspect the difference to be very small but finite.

Answer 8

The following article seems to support my intuition that higher frequency equates to higher inertia and lower speed.

http://www.universetoday.com/11889/high-energy-gamma-rays-go-slower-than-the-speed-of-light/

Answer 9

@Vinaire
In case you're looking for a theoretical proof -

"...In the early 1860s, Maxwell showed that, according to the theory of electromagnetism he was working on, electromagnetic waves propagate in empty space at a speed equal to the above Weber/Kohrausch ratio, and drawing attention to the numerical proximity of this value to the speed of light as measured by Fizeau, he proposed that light is in fact an electromagnetic wave..."

I don't know about the proof of Maxwell, but I think it should be similar to this -
Consider an electron being oscillated (by some external force) in the path
x=A sinωt

It will produce an oscillating current
i=Aω cosωt

Which will in turn produce an oscillating magnetic field >> oscillating electric field >> ...

You can use Ampere's circuital law (as extended by Maxwell) and Faraday's law of electromagnetic induction to find the equation of subsequent fields.

As speed of the wave can also be referred to as the rate of propagation of energy; try to find the energy associated with each of the subsequent fields. (Use the formulas of energy per unit volume; or whatever they are called)

If the rate of propagation of energy turns out to be independent of the frequency (and I think it will) we can say that all electromagnetic waves travel at the same speed.

I wish I could show the complete proof; but the integrals look somewhat laborious and I am short of time.

Please note that there is an obvious flaw in the above proof as we are not recognizing the wave-particle duality (but my analytical ability is restricted to classical physics).

As for the article you cited in the previous post; I wont comment on it as it is way beyond me.

Answer 10

As a follow-up question - In many books I read the phrase "Maxwell found an inconsistency with Ampere's circuital law...so he extended it to include displacement currents"

Can anyone explain what was that inconsistency?

Answer 11

@LastDayWork
Thank you for taking time to respond to my question. I am semi-retired (~68 years old) and trying to fill holes in my understanding of Physics. I graduated from MIT in 1971 with Master's in Nuclear Engineering.

I am not a physicist, but I am very interested in looking into the fundamentals of Physics starting from a broad picture and reading whatever I can on Internet. I got interested in the inconsistency of how light can travel in vacuum without a medium.

I am just a layman when it comes to Quantum mechanics. I am more of a classical enthusiast. The following conjecture is very nebulous, but it is currently guiding my search:
1. The universal field of modern aether is pre-spacetime.
2. Spacetime is generated from the disturbance of this universal field.
3. The fundamental harmonic of this disturbance manifests as the basic spacetime, where the frequency of the disturbance is close to zero, the wave-length is almost infinite, and the period is infinite too.
4. Subsequent harmonics have higher frequencies and shorter wavelengths and period. Each harmonic acts as an overlay of spacetime.
5. Increasing frequency generates increasing inertia.
6. At sufficient higher frequncies, inertia generates discreteness, such as that of photon.
7. At still higher frequencies and shorter wavelengths, inertia generates particles with mass.
8. There are particles of increasing complexity until electrons, protons and neutrons are generated.
9. Thus come about atoms, elements, the periodic table, the molecules and compounds.
10. And, so we have a universe of objects with forms.

I am trying to understand more about Inertia. It is manifested as mass for a particle, and I believe that it is manifested as frequency in case of the electromagnetic radiation. It seems to be that ELF shall propagate at a speed higher than that of light. I am searching for any data existing on this subject.

Answer 12

Dear OS Admins,

I am in "desperate" need of a tagging system which can provide precise information related to a user's area of expertise. This is to ensure that a "12th pass student" does not ends up "teaching relativity to Einstein".

Yours sincerely (maybe :D )
LastDayWork

Answer 13

Probably this is not the right forum for me.

Answer 14

Try talking to -
@UnkleRhaukus
@broken_symmetry
@Vincent-Lyon.Fr
@Mashy

Answer 15

How do I give a medal to you?

Answer 16

Q: As a follow-up question - In many books I read the phrase "Maxwell found an inconsistency with Ampere's circuital law...so he extended it to include displacement currents" Can anyone explain what was that inconsistency?"

A: Maxwell's equation without the displacement current are not consistent with the conservation of charge.

Answer 17

@Vincent-Lyon.Fr
I still don't see how conservation of charge is being violated (without displacement current).

Answer 18

If : \(\vec \nabla \times \vec B=\mu _o \vec j\) (pre Maxwell)

then \(\vec \nabla . \vec j=0\) which is in contradiction with conservation of charge
which requires that \(\vec \nabla . \vec j=-\partial \rho /\partial t\)

If : \(\vec \nabla \times \vec B=\mu _o (\vec j+\epsilon _o \partial \vec E /\partial t)\) (post Maxwell), then everything is ok.

Answer 19

Can you please upload a screenshot of the above post. It looks like -

Answer 20

Here it is: