OT:Tempted to get this book

[Fyron]

Kamog said:
A light beam shining through glass will slow down and it does speed up again once it exits the glass. Why does it speed up again when it exits the glass? That's a good question, and I don't know why. I'm very curious as to what the reason is. But I think the reason a block of glass will heat up when light is shined though it is because the glass is imperfect and not completely transparent. Part of the light is absorbed and turned to heat. So not all the light emerges from the other side.

It doesn't actually slow down, it just refracts within the glass and appears distored...

[Renegade 13]

Imperator Fyron said:

It doesn't actually slow down, it just refracts within the glass and appears distored...

Light does slow down through different mediums. If I recall correctly, light travels quite a bit slower through water than it does through a vacuum. Or it might be faster, I'm not sure. (If I'm totally wrong on this point, please correct me, but it seems to be what I remember from physics Last year). Therefore, the only thing that can exceed the speed of light, is light itself (depending on the medium)

[deccan]

Renegade 13 said:
Light does slow down through different mediums. If I recall correctly, light travels quite a bit slower through water than it does through a vacuum.

Yep, light can even be "stopped".

Scientists Bring Light to Full Stop, Hold It, Then Send It on Its Way

[Aiken]

Slowed light is virtual phenomenon. Once photon from light ray collides with atoms of medium it transfers its energy to atom and disappears, but atom goes to hugher energy state. After some time atom re-emits photon with similar wavelenght in the same (if medium has no lens ability) or different direction and then atom goes back to initial energy state. This effect will occur many times until photon leaves meduim. Since cycle of "absorbtion-reemission" is not instant, it gives effect of "slowed light".

edit: note, that it's a very primitive explanation which assumes that photon bahaves itself as a particle. But in real world it also behave itself as a wave. And things become slightly more complicated. But the principle remains the same.

[deccan]

aiken said:
Slowed light is virtual phenomenon. Once photon from light ray collides with atoms of medium it transfers its energy to atom and disappears, but atom goes to hugher energy state. After some time atom re-emits photon with similar wavelenght in the same (if medium has no lens ability) or different direction and then atom goes back to initial energy state. This effect will occur many times until photon leaves meduim. Since cycle of "absorbtion-reemission" is not instant, it gives effect of "slowed light".

Good explanation. Keep up the physics lessons!

[Renegade 13]

aiken said:
Slowed light is virtual phenomenon. Once photon from light ray collides with atoms of medium it transfers its energy to atom and disappears, but atom goes to hugher energy state. After some time atom re-emits photon with similar wavelenght in the same (if medium has no lens ability) or different direction and then atom goes back to initial energy state. This effect will occur many times until photon leaves meduim. Since cycle of "absorbtion-reemission" is not instant, it gives effect of "slowed light".

edit: note, that it's a very primitive explanation which assumes that photon bahaves itself as a particle. But in real world it also behave itself as a wave. And things become slightly more complicated. But the principle remains the same.

Ok, that makes sense. Based on your explanation, the speed of light in a vacuum is the "fastest" light can travel through any known medium, since there is virtually nothing to "slow" the light wave/particle. Therefore, the speed of light in a vacuum is the "fastest" anything can travel, as far as we know (disregarding certain quantum effects if my memory serves me well). I always knew that light behaved (under certain circumstances) as a particle and/or a wave. However, what significance does this have?

[Aiken]

Wave properties of light are responsible for things such as diffraction, interference and other physical phenomenons.

[Parasite]

Renegade 13 said:

Ok, that makes sense. Based on your explanation, the speed of light in a vacuum is the "fastest" light can travel through any known medium, since there is virtually nothing to "slow" the light wave/particle. Therefore, the speed of light in a vacuum is the "fastest" anything can travel, as far as we know (disregarding certain quantum effects if my memory serves me well). I always knew that light behaved (under certain circumstances) as a particle and/or a wave. However, what significance does this have?

The "Speed of light" numbers are really "The speed of light in a vaccuum" speeds. Strangely there are certian particles that can travel faster than the speed of light when this light is slowed by going through glass or air. This is one reason why Cherenkov detectors work.

[Renegade 13]

Parasite said:
The "Speed of light" numbers are really "The speed of light in a vaccuum" speeds. Strangely there are certian particles that can travel faster than the speed of light when this light is slowed by going through glass or air. This is one reason why Cherenkov detectors work.

Ah right, neutrinos and neutrino detectors would be what you're referring to. Neat little things aren't they?

[Aiken]

Parasite said:
Strangely there are certian particles that can travel faster than the speed of light when this light is slowed by going through glass or air. This is one reason why Cherenkov detectors work.

Faster than speed of light in medium. But particles causing Cherenkov radiation (like hi-energy proton) move slower than speed of light in vacuum anyway. So this is pseudo-FTL movement.