# Speeds of Light Colors

1. Jan 28, 2005

### Moe_the_Genius

Hi,
Are the speeds of all different colors of light exactly the same? And has this been done experimentally? Have they actually let colors into a system where it calculated its speed. (I know that Albert Michelson measured the speed of pure light_I just don't know if he or anyone else has done the same thing experimentally with light colors) Is there a site where I can find info on this?
Thanks a lot,
Mohammad

2. Jan 28, 2005

### Integral

Staff Emeritus
Yes the speed of light is indepentent of frequency (color). Yes it is well verified. Ever hear of a Laser?

3. Jan 28, 2005

### Glenn

Don't some VSL theories state that there are tiny differences between say red and purple light? So tiny that we can't measure them (yet?).

-Glenn

4. Jan 29, 2005

### Moe_the_Genius

What about it? I believe that the speed of light and laser vary by a tiny amount (and I believe that is significant in studying Physics). Is that right? I need expert confirmation on this.

5. Jan 29, 2005

### Staff: Mentor

No, it's not. The light produced in a laser travels at the same speed (in vacuum) as any other light.

Last edited: Jan 29, 2005
6. Jan 29, 2005

### Staff: Mentor

That's contradictory - if its a tiny amount, its not significant.
You got it!

7. Jan 29, 2005

### dextercioby

Look at it this way,like a person who's got good logics,but doesn't know physics at all:
"If laser woudn't travel at the speed of light,why did they call it "LASER" (apud L.A.S.E.R.) ?????????"

Daniel.

8. Jan 29, 2005

### rbj

based on such a premise, i would be skeptical.

r b-j

9. Jan 31, 2005

### Gonzolo

There is no difference if propagation takes place in a vacuum, where the refractive index is 1 for all wavelength.

If it travels in another medium, the refractive index is generally not 1, and varies with wavelength. This variation is called the dispersion relation. Air can be considered as such a medium, but it is sufficiently close to vaccum in most cases (1.00...something...).

The atmosphere is composed of various air compositions depending on location and time, so its exact dispersion relation is not trivial.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook