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