Which color is the fastest?

[beansbaxter]

Which color, between red and blue, is the fastest?

When the light bends through the prism, can we say that the red is the fastest? Nearly all the time, yes.

One particular kind of glass, for example, the index of refraction (c/v, where c is the speed of light in vacuum and v is the speed of a particular frequency of light in glass) is 1.514 for red light and 1.54 for blue light, so in this case the red light travels at c/1.51, and the blue light travels at c/1.54.

The result is that red light travels 2% faster than the blue light.

So does this mean that all things considered equal, red vehicles travel faster than blue vehicles?

 

[RaynorWolfcastle]

Depends on the nature of a dispersive medium, in a normally dispersive medium red is fastest whereas in a medium with anomalous dispersion blue will travel fastest. Typically there will also be dispersion related to the geometry of the waveguide and if you're really clever about it, you can design your waveguide in such a way that some frequency of interest shows a relatively flat index near the frequency of interest.

As for the part about the speed of red and blue vehicles, I'm supposing that was a joke?

 

[beansbaxter]

Originally posted by: RaynorWolfcastleAs for the part about the speed of red and blue vehicles, I'm supposing that was a joke?

Not really. Friend and I are very big into motorcycles. We often joke that one motorcycle is faster than the other simply based on color. Ya know "blue is the fastest color" when our motorcycles are identical aside from the red or blue color difference.

Then we did some research and found out that red light seems to be slightly faster than blue light. So it begged the question, is a red motorcycle faster than a blue motorcycle in the smallest possible measurement? If that makes sense...

I was talking to a professor at the college who works out at the gym with me, he was mentioning how there are studies where blue has been proven to be the fastest color, but it is based upon in depth research of aqua-dynamics blah blah blah...way over my head.

So I thought I'd ask the question here, see whatcha'll think.

 

[MrDudeMan]

the color of an object does not affect how fast it is going. it only affects how fast you see it.

 

[Bassyhead]

Originally posted by: Bigsm00th
the color of an object does not affect how fast it is going. it only affects how fast you see it.

Red is faster, think Ferraris. And cops love to pull over red cars so that proves red is definitely faster

 

[MrDudeMan]

Originally posted by: Bassyhead

Originally posted by: Bigsm00th
the color of an object does not affect how fast it is going. it only affects how fast you see it.

Red is faster, think Ferraris. And cops love to pull over red cars so that proves red is definitely faster

:beer:

 

[yosuke188]

Originally posted by: Bassyhead

Originally posted by: Bigsm00th
the color of an object does not affect how fast it is going. it only affects how fast you see it.

Red is faster, think Ferraris. And cops love to pull over red cars so that proves red is definitely faster

Why do you think cops have red and blue sirens? It's to make themselves faster!

 

[imported_Hamzter]

Well according to this advert from the 1990s, the blue car won (because the red car just couldn't carry on). End of discussion

 

[Mokmo418]

An object moving towards the observer will be a little redder than an object heading away from same observer which will be more blue. It's just like when a race car passes by, the pitch of the engine sound will lower.
It's called the doppler effect, applies to wavelenghts.

It's not that red light is faster, it's just that it has a shorter wavelenght.

 

[Polyfluoroethylene]

Originally posted by: beansbaxter
Which color, between red and blue, is the fastest?

When the light bends through the prism, can we say that the red is the fastest? Nearly all the time, yes.

One particular kind of glass, for example, the index of refraction (c/v, where c is the speed of light in vacuum and v is the speed of a particular frequency of light in glass) is 1.514 for red light and 1.54 for blue light, so in this case the red light travels at c/1.51, and the blue light travels at c/1.54.

The result is that red light travels 2% faster than the blue light.

So does this mean that all things considered equal, red vehicles travel faster than blue vehicles?

Not unless it's powered by light.

 

[unipidity]

You got that one inverted Mokmo. Incidentally.

Red light has a longer wavelength. And things moving towards you are blue shifted.

 

[rezinn]

You can have two identical motorcycles, all else equal, and one will always be faster due to production tolerances, you being fat, or what color socks you are wearing.

 

[Vee]

On a very wild hunch, I'd say blue is faster. Blue pigments generally absorb longer wavelengths better. That energy transfers into the thin turbulent boundary layer and possibly makes the surface a microscule bit more 'slippery'.

However, I'm very confident rezinn is right, and the socks you're wearing will be a much greater factor.

 

[gsellis]

Originally posted by: Hamzter
Well according to http://web.ukonline.co.uk/mark.mcmillan2/m_r/milky_way.rm">this advert</a> from the 1990s, the blue car won (because the red car just couldn't carry on). End of discussion

Yes, but the girl in the Red dress... Nevermind.

 

[spinaltap]

This isnt exactly a very technical question, persay, but here's the answer nonetheless:

In a vacuum all electromagnetic waves travel at the same speed, 3e8 m/s (c). Frequency determines differences in energy, which is observed as color in the visible part of the electromagnetic spectrum. Red has the lowest frequency, while blue/indigo/violet/whatever has the highest. Frequency, wavelength and velocity are related by the equation v = f*lambda, where lambda is wavelength. As you can see, wavelength is inversly proportional to frequency.

Changes in velocity for electromagnetic waves occurs when the light goes from one medium to another, called refraction. In space, v=c, but in other mediums this is not true. In other mediums, v=c/n where n is the index of refraction. n=1 in a vacuum and is >= 1 in all other mediums. The wavelength, lambda, relates to n, by the equation n=lambda(vacuum)/lambda(new medium). Frequency does not change between mediums.

Since both sides of the original equation are modified by the same number, n, it is easy to see that the velocity should be no different between different wavelengths of light. There is a difference, however, in the angle at which the light bends upon refraction; described in snell's law. It is this principle that makes prisms work the way they do.

That was probably a little longer than neccessary, but i was bored. Hope that helps.

 

[Parkre]

so if red and blue light are the same, why do the future dvds have blue leds??

 

[gsellis]

Originally posted by: Parkre
so if red and blue light are the same, why do the future dvds have blue leds??

Smaller wavelength, hence smaller "write/read" area. Put stuff closer together and make the pits smaller.

 

[RaynorWolfcastle]

Originally posted by: Parkre
so if red and blue light are the same, why do the future dvds have blue leds??

The resolving power you have for features is a roughly linear function of the wavelength you are using (or roughly inversely proportional to the laser spot size). So by using blue-violet lasers that have a wavelength in the 400nm range instead of the 650nm red lasers used in DVD they can reduce the "pit" size.

You can also decrease the spot size of the laser you shine by increasing the NA (numerical aperture) of the optics which they also did (0.85 for Blu-Ray vs 0.6 for DVDs).

as an aside, all data drives I've ever heard of use laser diodes, not LEDs

 

[gsellis]

Originally posted by: RaynorWolfcastle

Originally posted by: Parkre
so if red and blue light are the same, why do the future dvds have blue leds??

The resolving power you have for features is a roughly linear function of the wavelength you are using (or roughly inversely proportional to the laser spot size). So by using blue-violet lasers that have a wavelength in the 400nm range instead of the 650nm red lasers used in DVD they can reduce the "pit" size.

You can also decrease the spot size of the laser you shine by increasing the NA (numerical aperture) of the optics which they also did (0.85 for Blu-Ray vs 0.6 for DVDs).

as an aside, all data drives I've ever heard of use laser diodes, not LEDs

Not to RaynorWolfcastle, just adding

Pioneer mentioned about a year ago that they were working on UV lasers for discs. I think I remember double-side, double-layer expected to reach .5TB. UV is shorter than Blue.

 

[Parkre]

Originally posted by: RaynorWolfcastle

Originally posted by: Parkre
so if red and blue light are the same, why do the future dvds have blue leds??

The resolving power you have for features is a roughly linear function of the wavelength you are using (or roughly inversely proportional to the laser spot size). So by using blue-violet lasers that have a wavelength in the 400nm range instead of the 650nm red lasers used in DVD they can reduce the "pit" size.

You can also decrease the spot size of the laser you shine by increasing the NA (numerical aperture) of the optics which they also did (0.85 for Blu-Ray vs 0.6 for DVDs).

as an aside, all data drives I've ever heard of use laser diodes, not LEDs

Thanks

and sorry, I realized my mistake after I posted. It's hard to get a laser from a LED.

 

[Finns14]

Did you know that some red cars are more expensive to insure because people tend to drive red cars fast??????

 

[imported_BigT383]

Well, because of the refraction index, Red light will move through the air faster than blue, but blue has a higher energy.

So technically riding up over a hill in the road the red motorcycle would come into view first, but the blue motorcycle is more likely to be noticed since the light from it would have more energy with which to trip the detector...

 

[makken]

i actually heard yellow cars get pulled over the most >_<

 

[glugglug]

Blue car is faster, because the red car spends too much time getting pulled over.

And this is an absolute fact. With only one exception, every ticket I have ever gotten has been with a red vehicle. Including 2 on a red bicycle.

 

[Born2bwire]

The different velocities of light in a prism are a result of the dispersive nature of the medium. Air is not considered to be dispersive within the visible range. So in most situations, we cannot say that one color is faster over another.