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16 years ago
#41
(Original post by marcos)
(Newton's laws imply the wave nature of light).
Maxwell's equations imply that light is an EM wave, surely.
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16 years ago
#42
(Okay and there've been about 500 posts since I started writing up my last one! )
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16 years ago
#43
Yeah what I meant was that there's no mention of the particle nature of light through Maxwell's/Newton's Laws (ie. also special relativity since it's basically an extension of Maxwell's equations)
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16 years ago
#44
(Original post by dinkymints)
Thanks all. I know I don't need to know all of this but I'm interested... my teacher refuses to answer my questions, I get at least one "I'm not telling you coz it's too hard and it's not on the syllabus" per lesson. It's kind of annoying that we have to learn that things happen and not why, for example why moving a wire through a magnetic field produces a current.

One more question... in our mock paper, one of the questions mentioned that there used to be debate as to whether light acted as a wave or particles and that now it is known that it acts as both. (Very simply put, as the question wasn't really about that at all but about ideas and evidence blah blah). So I was wondering whether light is affected by gravity, if it behaves as a particle? Somebody mentioned in this thread that gravity acts on all things with mass - light doesn't have mass, does it? So I assume that's a no?
Basically, the wire in a magnetic field moves because the magnetic field around the wire (right hand grip rule) and the other magnetic field interact. On 1 side of the wire they reinforce and on the other they cancel each other out so there is a net force pushing it sideways.

Photons of light have no rest mass but are still affected by gravity. We have found some black holes cos of gravitational lensing - light from a star behind the black hole being bent so much that we see it twice because we have light being bent round both sides of the black hole. How they know its the same star as opposed to 2 similar ones I haven't a clue!
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16 years ago
#45
yeah, you gotta keep up! short posts are the only ones which will do lol
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#46
Thanks all... much more helpful than my physics teacher!!

I *know* I won't be asked it, I am just curious and yes I know it killed the cat

It's "she", by the way.
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16 years ago
#47
(Original post by dinkymints)
Thanks all... much more helpful than my physics teacher!!

I *know* I won't be asked it, I am just curious and yes I know it killed the cat

It's "she", by the way.
Oooops!! Sowee, i didnt know. Ill remember, for now
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#48
lol, that's ok!
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16 years ago
#49
This thread has been reaaaaaaaally fast, only been 53 mins and 3 pages already lol. Im gonna go now tho, TV series on the chinese channel...im addicted
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16 years ago
#50
(Original post by kenkennykenken)
This thread has been reaaaaaaaally fast, only been 53 mins and 3 pages already lol. Im gonna go now tho, TV series on the chinese channel...im addicted
have fun i have a driving test tomorrow
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16 years ago
#51
Good luck! I failed mine lol
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16 years ago
#52
(Original post by kenkennykenken)
But curiousity killed the cat!
not if it belonged to schroedinger
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16 years ago
#53
Oh don't get onto that, we'd be hear all day! lol!!!!
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16 years ago
#54
(Original post by diablo2004)
not if it belonged to schroedinger
His equation is scary.
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#55
I've found a definition of the Universe as where light has shone out to so far. So does that mean if the Big Crunch happens, light will turn back on itself?
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16 years ago
#56
(Original post by Nylex)
Maxwell's equations imply that light is an EM wave, surely.
Aha, but if it has no mass, how can it have energy?
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16 years ago
#57
(Original post by mik1a)
Aha, but if it has no mass, how can it have energy?
The equation E^2 = mc^2 = p^2c^2 + (m0c^2)^2 tells us it has energy. m0 = rest mass. Photons have no rest mass, but can still have energy because they have momentum (therefore they have kinetic energy).

That equation simplifies to E = pc for a photon. Oh yeah, even though p = mv, photon's do have momentum, which is given by p = h/lamda (lamda = wavelength, h = Planck's constant 6.63... x 10^-34 Js).

Edited again.
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16 years ago
#58
E=pc
p=mv
E=mvc
v=c with a photon, so
E=mc^2.

But k.e = 0.5mv^2

where does the other 0.5mv^2 go? or does that equation not apply to a photon.

edit - oh, missed your edit. maybe that makes this wrong!
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16 years ago
#59
(Original post by mik1a)
E=pc
p=mv
E=mvc
v=c with a photon, so
E=mc^2.

But k.e = 0.5mv^2

where does the other 0.5mv^2 go? or does that equation not apply to a photon.

edit - oh, missed your edit. maybe that makes this wrong!
I think it doesn't work because you can't use p = mv for a photon, as they have 0 rest mass. Not too sure, relativity and quantum mechanics are hard to understand.
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16 years ago
#60
You're telling me.
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