Light - Momentum and Energy

[abygael]

Someone asked this question on my last/first sciencey post. I decided that it was too long an answer to just leave in the comments, so here it is, question and answer:

Question: What happens to light (a photon) as it passes through a transparent medium? We know that photons do not have a mass, however they do have energy and momentum. If we

Comments

[anonymous]

Ahh, the one thing I hate about physics: choose the model which suits us best :P But thanks for answering my question. As an engineer looking towards alternative energy sources for vehicles, light energy is certainly an intriguing path to follow :)

Brendan (friend of Jo (twelveeyes) who really should get an LJ account because he keeps commenting and forgetting to leave a by-line)

[jeebuz_avt]

Your mind can be broken further when you learn that there IS a unified wave/particle model, which relies on probabilistic principles.

Also, you lazy bastard, give us Hydrogen Fuel Cells and Positive energy Nuclear Fusion faster! FASTER! STOP LOOKING TO THE SUN IT JUST BURNS

[abygael]

Well, you couldn't use light to power a vehicle on Earth, becasue sunlight is reflected from every-which-where and wouldn't actually end up pushing in any specific direction. Even in space it's effectiveness is ambiguous because a) really big solar sails are required to get anywhere and b) once you get far from the sun (even as close as Jupiter, I suspect, though don't quote me on that one), it stops having enough power to accelerate a ship and said ship would have to rely on other energy sources to turn, break, etc.

[jeebuz_avt]

If you're careful about picking your gravity wells though, you'll only need patience and a little bit of reaction mass to get where you're going.

And if chemistry was of any use you'd have given me a better material than silicon with it's crappy work function. WHERE IS MY BETTER MATERIAL? HUH?

[markdeniz]

Greeting from a fellow purple zoner, thanks for letting me know about your LJ and maybe you can teach me a bit about science over the next few posts!

*winks*

[abygael]

Cheers.

I'll do my best :-)