Light Travelling Through Space.

[Wearden]

Hey Guys, Awhile ago, My class was studying a little on space.

They werent the most satisfying lessons but they did well, We were all learning about how light travelling through the Atmosphere and around the earth.

My science teacher said "Light needs particles/Something to travel through", This does not describe how light travels through space.

Correct me if i am wrong but i though Space was a 'Vaccum', My teacher said there is no particles present... So how does light travel from the sun to the Atmosphere and so on?

 

Thanks..

Ben.

[Sisyphus]

Light does not need a medium to travel through. Either you misunderstood what your teacher was saying, or your teacher was very, very wrong.

[spikerz66]

To put it bluntly, your teacher was wrong. Light doesent need ANYTHING to travel through. Light is photons. Infact the speed of light © is slowed down in the earths atmosphere, where does the reamaining part of light go? Its turned into thermal energy.

[Klaynos]

To put it bluntly, your teacher was wrong. Light doesent need ANYTHING to travel through. Light is photons. Infact the speed of light © is slowed down in the earths atmosphere, where does the reamaining part of light go? Its turned into thermal energy.

 

So I shine a light beam into a rectangle of glass, it slows down (refracts) and comes out the other side, speeding up and refracting again.

 

Are you telling me the thermal energy magically jumps from one side to the other of the solid and rejoins the photons?

 

As above, light needs no medium in which to travel it is one of the things which makes it so unusual... It is a combination of self propagating bootstrapping electric and magnetic fields (don't worry most physics undergrads don't understand this either)

[spikerz66]

i apologise my brain was going to fast

[swansont]

So I shine a light beam into a rectangle of glass, it slows down (refracts) and comes out the other side, speeding up and refracting again.

 

Are you telling me the thermal energy magically jumps from one side to the other of the solid and rejoins the photons?

 

But there should be an interesting effect: because the momentum of the photons change there should be a force on the medium. If we do this with a long optical fiber, there should be a strain on it when the photons enter one end, but before they leave the other. Someone told me about a proposed experiment to measure this, but I can't recall who was proposing it, or find any results. But I know that Ketterle's group at MIT measured the recoil momentum of photon absorption in a gas to be [math]n\hbar k[/math] rather than [math]\hbar k[/math], which is the same idea.

[Wearden]

Aah, Thanks people. I'll go give my science teacher a 'Lecture' about light, Photons and Thermal energy now.. He needs it! ^^

All the best..

Ben.