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Speed Of Light X Ray

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Does this hateful the speed of 10 ray faster than light in vaccum

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http://global.britannica.com/EBchecked/topic/495677/refractive-index
refractive alphabetize, besides called index of refraction, measure of the bending of a ray of calorie-free when passing from one medium into another. If i is the angle of incidence of a ray in vacuum (angle between the incoming ray and the perpendicular to the surface of a medium, chosen the normal; encounter effigy) and r is the angle of refraction (bending between the ray in the medium and the normal), the refractive index n is defined every bit the ratio of the sine of the bending of incidence to the sine of the angle of refraction; i.e., north = sin i / sin r. Refractive index is also equal to the velocity c of light of a given wavelength in empty space divided by its velocity five in a substance, or n = c/v.

Some typical refractive indices for yellow light (wavelength equal to 589 nanometres [10−9 metre]) are the following: air, 1.0002; water, 1.333; crown glass, 1.517; dense flint drinking glass, i.655; and diamond, ii.417. The variation of refractive index with wavelength is the source of chromatic aberration in lenses. The refractive alphabetize of X-rays is slightly less than one.0, which ways that an X-ray inbound a piece of drinking glass from air will be bent away from the normal, different a ray of light, which will be bent toward the normal. The equation n = c/v in this case indicates, correctly, that the velocity of X-rays in glass and in other materials is greater than its velocity in empty space.

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Answers and Replies

The stage velocity in matter tin exceed the speed of light in vacuum. It does not transmit any data, however.
Even the grouping velocity tin can do this in some rare circumstances (with high assimilation in the fabric).
The bespeak speed ("how fast can I transmit data") cannot exceed the speed of light.

In vacuum, all three speeds are the same. In affair, things are more than complicated.

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To add to what mfb said, I'thou pretty sure the just way you could apply the phase velocity to transmit information would be to notice changes in the phase velocity. Those changes will propagate at a speed less than or equal to the speed of light in whichever medium you're considering.
The stage velocity in affair can exceed the speed of calorie-free in vacuum. Information technology does not transmit whatsoever information, however.
Even the grouping velocity tin can do this in some rare circumstances (with high absorption in the fabric).
The signal speed ("how fast tin I transmit data") cannot exceed the speed of light.

In vacuum, all three speeds are the same. In matter, things are more complicated.


thank you for your answer. "phase velocity in matter can exceed the speed of light in vacuum" .Does this violate special relativity in which the speed of light in vacuum is the limit of speed? why?
PS:why " It does not transmit any data"?
Does this violate special relativity in which the speed of light in vacuum is the limit of speed?
No. Special relativity puts a limit on the signal speed.
" Information technology does not transmit whatever information"?
To get a propagating phase at some point, you need the bespeak ("information") to arrive (slower than calorie-free) first.
cheers for your respond. "stage velocity in matter can exceed the speed of light in vacuum" .Does this violate special relativity in which the speed of calorie-free in vacuum is the limit of speed? why?
PS:why " It does not transmit whatsoever data"?
A picture is worth a yard words.

Look at the centre-left figure below, where the phase velocity is greater than the group velocity. The cherry dot indicates the phase velocity, moving forth with the elevation of a wave.

Simply the betoken or pulse (i.eastward. the data) is represented by the broad peak enveloping the group of waves. It travels more than slowly than the phase velocity, and the blue dot indicates how fast this travels every bit it moves forth with the signal pulse.

littlewavepackets.gif
(from this web page)
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No. Special relativity puts a limit on the indicate speed.

To get a propagating phase at some point, you need the signal ("information") to go far (slower than light) showtime.


thank you! what does "velocity of 10-rays in glass " mean ? phase velocity or group velocity?
by the style, I don't say about wave packet,I just say plane wave(x ray wave). Does airplane wave
have group velocity ?
cheers! what does "velocity of 10-rays in drinking glass " mean ? phase velocity or group velocity?
There is no single "velocity of [whatsoever] in drinking glass", that is exactly my point.
by the way, I don't say about wave packet,I just say plane wave(x ray wave). Does aeroplane moving ridge
accept group velocity ?
Well, you can all the same calculate the group velocity, but a airplane wave volition be contained of that.
A moving picture is worth a k words.

Wait at the eye-left figure beneath, where the stage velocity is greater than the grouping velocity. The reddish dot indicates the phase velocity, moving along with the top of a moving ridge.

But the betoken or pulse (i.e. the information) is represented past the broad elevation enveloping the grouping of waves. It travels more than slowly than the phase velocity, and the blue dot indicates how fast this travels equally information technology moves along with the signal pulse.

[PLAIN]http://resource.isvr.soton.ac.uk/spcg/tutorial/tutorial/Tutorial_files/littlewavepackets.gif[/INDENT][/INDENT] [Cleaved]
(from this web folio)​

Thank you!! The equation northward = c/v in this example indicates, correctly, that the velocity of Ten-rays in drinking glass and in other materials is greater than its velocity in empty space. if we consider plane wave,not wave parcel, is this correct? I don't understand why the velocity of 10 ray can surpass light in vaccuum! cheers!!​

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if we consider plane wave,not moving ridge packet, is this correct? I don't empathise why the velocity of x ray can surpass calorie-free in vaccuum! thanks!!
Some specific speed in the clarification of the airplane wave (the stage velocity) is faster than light. This is not the move of annihilation! The phase velocity is not restricted in whatsoever mode - information technology can even go backwards.

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Speed Of Light X Ray,

Source: https://www.physicsforums.com/threads/does-this-mean-the-speed-of-x-ray-faster-than-light-in-vaccum.676503/

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