| |
| |
| |
|
Page: 1 2 3 4
Comments:
<defcon8> there was a free physics book about everything and it was about 128mb pdf. does anyone know it? (i know this is amiguous but someone might know)
<defcon8> it had its own site
<JohnFlux> When a light wave goes through space..
<JohnFlux> it waves up and down
<JohnFlux> so.. does it actually move up and down?
<JabberWalkie> and sticks its left foot in...
<JabberWalkie> and it shakes it all about...
<JohnFlux> or is it just the intensity of the electric field that changes?
<JohnFlux> or does it actually move through space up and down
<JohnFlux> also, how thick is it?
<JohnFlux> you always draw light waves as having a polarisation, and it seems infinitely flat
<JohnFlux> how flat is it? does it makes sense to ask?
<NoorulIslaam> JohnFlux the lightwave *is* an electric and magnetic field (electromagnetic field)
<NoorulIslaam> there are different polarizations
<JohnFlux> NoorulIslaam: right.
<NoorulIslaam> one is a circular polarization
<NoorulIslaam> if you looked at the wave from up front
<NoorulIslaam> it would be a circle
<JohnFlux> NoorulIslaam: what would be a circle
<JohnFlux> the intensity of the electric field?
<NoorulIslaam> the electromagnetic field
<NoorulIslaam> it's vector would rotate and make out a circle
<JohnFlux> so the electric field is moving in space?
<NoorulIslaam> yes
<JohnFlux> by how much?
<NoorulIslaam> at the speed of light
<JohnFlux> can you state the amplitude in meters ?
<JohnFlux> of the light wave?
<NoorulIslaam> and the rate of the spin around the center if you looked at it from up front
<JohnFlux> not the rate of spin
<NoorulIslaam> is the frequency of the wave
<JohnFlux> the radius of that circle
<NoorulIslaam> yes
<JohnFlux> how big is that circle
<NoorulIslaam> f = c/r
<NoorulIslaam> i mean..
<NoorulIslaam> f = c/lambda
<NoorulIslaam> the length is the wavelength...lambda in that equation
<NoorulIslaam> and the radius is the wavelength divided by 2pi
<JohnFlux> so the intensity of the electric field
<JohnFlux> is that constant?
<NoorulIslaam> it varies in time
<NoorulIslaam> that's why you get a wave
<NoorulIslaam> it's actually a vector that's spinning around the center
<NoorulIslaam> if you look at it sideways
<NoorulIslaam> you see a sine wave
<JohnFlux> but you _also_ get a wave in the fact that it's physically moving in space
<JohnFlux> ?
<NoorulIslaam> that is the reason you get a wve
<NoorulIslaam> wave*
<NoorulIslaam> because it's moving
<JohnFlux> you just said it was because the intensity was changing
<JohnFlux> couldn't you have say it moving in space, but the intensity not changing
<NoorulIslaam> and why does that happen?
<NoorulIslaam> it's a combination of two things that trace out a sine wave in space
<JohnFlux> i think it just decays?
<NoorulIslaam> the fact that the photon is moving
<NoorulIslaam> and the fact that the electric field is rotating about the axis of movement
<JohnFlux> so does the photon physically whizz back and forth?
<NoorulIslaam> back and forth?
<NoorulIslaam> no
<NoorulIslaam> it just spins and moves forward
<JohnFlux> the photon goes in a straight line?
<NoorulIslaam> like the propeller of an airplane
<NoorulIslaam> yes
<NoorulIslaam> unless it's bent by gravity
<JohnFlux> it spins on its axis?
<NoorulIslaam> yes
<NoorulIslaam> that's what i just said
<NoorulIslaam> it spins about the axis of movement
<JohnFlux> but you also said the wave physically moves in sapce
<NoorulIslaam> it does of course
<JohnFlux> take like a radio wave
<JohnFlux> meters big
<NoorulIslaam> yep
<JohnFlux> does a radio wave photon move left and right a few meters as it travels forward
<NoorulIslaam> no
<JohnFlux> or does it stay still horizontally, and only move forward?
<NoorulIslaam> it moves forward and spins at the same time
<JohnFlux> how big is a radio wave photon?
<JohnFlux> :0
<JohnFlux> meters big?
<NoorulIslaam> depends on the frequency
<JohnFlux> or tiny tiny thing?
<NoorulIslaam> yeah meters big
<JohnFlux> hmm
<JohnFlux> oh that answers my question actually
<JohnFlux> so when you consider the wave, the photon is the whole thing really
<NoorulIslaam> of course
<JohnFlux> I always thought it was a tiny point on the wave
<NoorulIslaam> the photon is one complete cycle of the wave
<JohnFlux> hmm a radio wave photon is meters big
<JohnFlux> oh
<JohnFlux> hmm
<JohnFlux> that's crazy to think about
<NoorulIslaam> why?
<NoorulIslaam> makes sense
<JohnFlux> take a polarised radio wave
<NoorulIslaam> ok
<JohnFlux> so you have this photon which is meters wide
<JohnFlux> what's it's thickness?
<NoorulIslaam> that depends on the polarization
<JohnFlux> perfectly horizontally polarised
<NoorulIslaam> if you're using a dipole antenna
<NoorulIslaam> the polarization is a flat line
<JohnFlux> how flat?
<NoorulIslaam> instead of being ellipitical or circular
<NoorulIslaam> completely flat, for an ideal antenna
<JohnFlux> so this photon is infinitely flat?
<JohnFlux> perhaps some planks constant flat or something?
<NoorulIslaam> but you'd have to be using an antenna that transmitted in one direction only
<JohnFlux> i don't care about how to make it
<JohnFlux> could you get this photon to be infinitely flat, but 2 meters wide?
<NoorulIslaam> theoretically, yes
<JohnFlux> so what if this photon rotated now?
<JohnFlux> slowly in time
<JohnFlux> but remaining infinitely flat
<NoorulIslaam> it would have a very low frequency
<JohnFlux> it's still moving forward
<JohnFlux> do you get rotating polarised waves?
<NoorulIslaam> well actually if the photon is linearly polarized
<NoorulIslaam> then it can't rotate
<JohnFlux> right
<JohnFlux> why not?
<NoorulIslaam> unless it gets refracted or reflected
<JohnFlux> why can't it rotate?
<JohnFlux> I'm imaging this big flat pancake photon
<JohnFlux> why can't it rotate?
<NoorulIslaam> it's not shaped like a circle
<NoorulIslaam> only circularly polarized photons are shaped like that
<JohnFlux> what is it shaped like?
<NoorulIslaam> this one is shaped like a flat line
<fritobandito> man, special relativity is such a trip
<JohnFlux> NoorulIslaam: say it's moving forward
<JohnFlux> NoorulIslaam: horizontally, it's like a meter wide
<NoorulIslaam> yes
<JohnFlux> NoorulIslaam: vertically, it has no height
<NoorulIslaam> it won't be rotating
<JohnFlux> now forwards, it's size is one period, right?
<NoorulIslaam> but the electric field will be travelling up and down horizontally
<JohnFlux> its
<NoorulIslaam> yes
<NoorulIslaam> it's one period of the electric field
<JohnFlux> so this photon is like a flat square
<JohnFlux> or flat circle
<NoorulIslaam> yeah
<JohnFlux> okay.
<JohnFlux> why couldn't it have some rotational momentum
<NoorulIslaam> because it's linearly polarized
<JohnFlux> this big flat pancake turning in time
<NoorulIslaam> it's not a pancake
Return to
#physics
or
Go to some related
logs:
gl_gears
#linux
#lgp
01005e000001
#proftpd
Sanhux
gdm hang
goxen import
#python
toutch boobs
|
|
