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Discovery consists of seeing what everybody has seen and thinking what nobody has thought. ..."Albert von Szent-Gyorgyi(1893-1986, 1937 Nobel Prize for Medicine, Lived to 93)"

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 Author Topic: how does light (EM wave[s]) travel through no media?  (Read 39701 times) 0 Members and 1 Guest are viewing this topic. Click to toggle author information(expand message area).
amarMabbu
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 « Embed this message on: November 23, 2008, 06:33:53 pm »

it is accepted that electromagnetic (EM) waves can travel through vacuum (absence of media), right? if they are indeed waves in literal sense, then shouldn't they need a medium for transmission?

so, then the riddle is how do they (light included) travel in vacuum?
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Fu-Kwun Hwang
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 « Embed this message Reply #1 on: November 23, 2008, 11:18:26 pm »

Changing magnetic flux will produce electric field in the near space, and changing electric flux will produce magnetic field in the near space. No other media is required.

So changing electric field at one point A produce changing magnetic field at near by point B, and changing magnetic field at point B will produce changing electric field at near by point C, ... so EM wavr is formed.

I assume you already understand the meaning of wave. And light is electromagnetic wave.
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amarMabbu
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 « Embed this message Reply #2 on: November 24, 2008, 04:57:22 pm »

i do realize no other media is necessary, like when light can pass through a jar of vacuum. but i don't understand how it can transmit through no media. i can very well visualize a physical particle moving/streaking through no media just by virtue of it initial momentum.

i guess one of the issues i'm finding it hard to reconcile is that waves have been generally taught as disturbance travelling through a medium, where the disturbance in the form of energy is transmitted from one particle to the adjacent one.

for the sake of discussion, i'll propose this set up. consider an opaque plastic/metal pipe of 1m diameter. now, consider one particular stretch of the pipe of length, say 10m, is transparent and the boundaries of that length are sealed off by glass plates. imagine the glass plates being perpendicular to the axis of the pipe. now consider the space bounded by the transparent tube and the glass plates was emptied out, i.e. creating vacuum in that region. now stream red light from one end of the pipe. i believe the red light will pass through that transparent section of the pipe with vacuum and can be see at the other end of the pipe. let's assume the pipe is not bent.

now i fail to understand how light that might be travelling either as particles (photons) or as waves up until the first glass plate travels through the vacuum.

could u explain what happens @ the first glass plate? i want to thank you for your time and energy answering my posts in advance.
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amarMabbu
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 « Embed this message Reply #3 on: November 24, 2008, 05:10:03 pm »

is it possible that light travels as 100% photons while in vacuum/empty space? or 4 that matter, all EM waves get converted to energy transfer particles or photons at the boundary of matter/vacuum [this boundary is itself a stretch of imagination, even if one can come up with a clean, well defined boundary] by some mechanism until it reached the next vacuum/matter boundary, at which point it can be easily seen to travel in dual forms?
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amarMabbu
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 « Embed this message Reply #4 on: November 24, 2008, 05:28:51 pm »

to rephrase my Q, is it only on account of empirical evidence that we accept light and EM waves travel through vacuum or is the actual propagation mechanism understood.

to give an analogy, it is my understanding that, it is only on account of empirical evidence that we accept that the speed of light is a constant and not because we can explain why it has to be 3x108 m/sec.

is the propagation of EM waves in vacuum/no media similarly on account of empirical evidence?
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Fu-Kwun Hwang
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 « Embed this message Reply #5 on: November 24, 2008, 08:50:05 pm »

From my personal view: wave is a disturbance travelling through space (not media). But there is a time delay dt which is propotional to distance  between two points dx.

dx= v*dt; where v is the speed of the wave.
Please check out formation of wave

For water wave, it is the disturbance of water. For sound wave, it is the disturbance of air.
For light or EM wave, it is a disturbance of both electric field and magnetic field.

The velue of speed of light in vacuum will be another value if we change the definition of "meter" and "second".
It is a result from experimental measurement.
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amarMabbu
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 « Embed this message Reply #6 on: November 25, 2008, 12:00:20 am »

i still have Q's, but i'll come back to them later after i do some more reading. in the mean time, could you throw some light on the following Q's?

1.is it known what proportion of light (em waves) travels as particles & what proportion of light travels in the wave form?
2.is it known what factors effect whether light (em waves) is produced as particles or waves and in what proportion?

regards,
amar
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Fu-Kwun Hwang
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 « Embed this message Reply #7 on: November 25, 2008, 09:06:15 am » posted from:Taipei,T'ai-pei,Taiwan

In our everyday life: most of the element behavior like either particle (or group of particles)  or wave.
And we tend to interpret all the system in term of particle or wave.

For visible light or energy less than visible light, we will find it's wave properties easily.

However, for very high energy gamma ray (especially paused gamma ray). we will find it behavior more like particle.

If an experiment was designed to measure wave property: we will find it's wave property.
If an experiment was designed to measure particle property: we will find it's particle property.
So it depend how you look at it (measure it).
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lookang
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http://weelookang.blogspot.com

 « Embed this message Reply #8 on: November 25, 2008, 11:05:03 am » posted from:SINGAPORE,SINGAPORE,SINGAPORE

This is a video i showed in class for the wave particle duality http://en.wikipedia.org/wiki/Wave%E2%80%93particle_duality in physics.

I believe it helps in
1. visualization of the phenomenon wave particle duality.
2. increasing interest of subject matter.

 « Last Edit: November 27, 2008, 07:46:44 am by lookang » Logged
amarMabbu
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 « Embed this message Reply #9 on: November 25, 2008, 01:35:00 pm »

enlightening video, nice find.
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lookang
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http://weelookang.blogspot.com

 « Embed this message Reply #10 on: November 25, 2008, 03:32:50 pm » posted from:SINGAPORE,SINGAPORE,SINGAPORE

ya!!....as teacher, i try to inspire students and motivate them to want to find out more.

glad to help
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amarMabbu
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 « Embed this message Reply #11 on: November 26, 2008, 09:00:57 pm »

1. just like how, it helps to visualize/understand gravity by considering it as a deformation of the fabric of space time by a heavy object (planets, stars, black holes...), even though it is a simplistic visualization, is there a way to visualize/understand electrical & magnetic fields/forces?

2. i personally think the deformation of space time fabric visual is very simplistic, only bcoz, only one plane, the horizontal one is depicted, in which more deformation is caused by, say body X and body Y experiences gravitation force towards X . but objects, say Z, that might be in other planes (for example say a few km right above the N pole of X) would also experience gravitational tug of X. is there any simulation/diagram that can do justice, visually, to imagining the deformation of the space time fabric all around the body X?
 « Last Edit: November 26, 2008, 09:19:10 pm by amarMabbu » Logged
lookang
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http://weelookang.blogspot.com

 « Embed this message Reply #12 on: November 27, 2008, 08:39:54 am » posted from:SINGAPORE,SINGAPORE,SINGAPORE

http://users.hartwick.edu/hartleyc/oneOverR/oneOverR.html

1/r Gravitational Potential & Orbiting Object
nice visualization for Gravitational Potential, is it similar enough for space time fabric?
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amarMabbu
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 « Embed this message Reply #13 on: November 27, 2008, 11:56:18 am »

again, another nice find.

this kind of explains, why the orbits of the our sun's planets seem to be sit on the same plane. also, this only makes me wonder even more, since this visualization kind of posits only one space time fabric. i wonder, if in reality, it that simple.

one interesting thought is, how does the gravitational field looks a few hundred km below this plane? hmm... imagine firing off a space ship or a probe, say straight down from the South pole of the earth. would it then just tear through the space time fabric?

i have lots more queries, but i'll let them distill b4 i post them.
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amarMabbu
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 « Embed this message Reply #14 on: November 27, 2008, 01:40:27 pm »

how does the lat simulation from hartwick univ explain the trajectories of, say comets, whose paths might be in planes that are at an angle to the plane of the space time fabric depicted in the simulation?

any ideas?
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lookang
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http://weelookang.blogspot.com

 « Embed this message Reply #15 on: November 27, 2008, 02:44:29 pm » posted from:SINGAPORE,SINGAPORE,SINGAPORE

Orbits in Strongly Curved Spacetime ..... this is really cool applet!
http://www.fourmilab.ch/gravitation/orbits/

What about comets:
actually it is "trapped" in the potential well, so a comet is also obeying the planets' gravitational potential field.
Look closely at the satellite when it is very near Earth, it "spun" out further but only to come back eventually due to weak influence far away.

My Understanding:
Actually, i don't really know space-time curvature.

What i roughly know is
curved space-time explains why if the sun disappears immediately, it takes 8+ minutes for the gravitational potential of the loss of the SUN to affect the earth's motion because space and time is like this giant web connecting objects and events like (x,y,z,t).

http://en.wikipedia.org/wiki/Spacetime
In spacetime, a coordinate grid that spans the 3+1 dimensions locate "events" (rather than just points in space), so time is added as another dimension to the grid.
 « Last Edit: November 27, 2008, 03:13:06 pm by lookang » Logged
amarMabbu
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 « Embed this message Reply #16 on: November 27, 2008, 04:35:05 pm »

yup, pretty cool animation. my kudos & sincere appreciation to all who've put in time & energy into these simulations and those who've developed the theories behind them, including mr. Hwang.

it'll take me some time 2 digest the info overload from the link u've just posted. in the meantime, what abt this?

1. one interesting thought is, how does the gravitational field looks a few hundred km below this plane? hmm... imagine firing off a space ship or a probe, say straight down from the South pole of the earth. would it then just tear through the space time fabric?
 « Last Edit: November 27, 2008, 04:40:20 pm by amarMabbu » Logged
Fu-Kwun Hwang
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 « Embed this message Reply #17 on: November 27, 2008, 04:40:00 pm » posted from:Taipei,T'ai-pei,Taiwan

Registed user can get files related to this applet for offline access.
Problem viewing java?Add http://www.phy.ntnu.edu.tw/ to exception site list
If java program did not show up, please download and install latest Java RUN TIME

I just create an EJS version of similar applet.
You can use mouse to drag the velocity vector to change the direction and magnitude of the velocity vector. Enjoy!

Registed user can get files related to this applet for offline access.
Problem viewing java?Add http://www.phy.ntnu.edu.tw/ to exception site list
If java program did not show up, please download and install latest Java RUN TIME
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amarMabbu
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 « Embed this message Reply #18 on: November 27, 2008, 04:41:24 pm »

sweet! thank u, mr. Hwang.
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amarMabbu
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 « Embed this message Reply #19 on: November 27, 2008, 04:52:18 pm »

that looks like the force field of a black hole, only that black holes seem to have one more funnel on the other end. hmm... more food 4 thought.
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amarMabbu
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 « Embed this message Reply #20 on: November 27, 2008, 04:54:54 pm »

cool, mr. Hwang. ur simulation has the other funnel on the bottom too! only i can't get it to play yet. but i'll figure it out, how to play the simulation.

this is exactly the kind of space time fabric curvature/deformation i wanted to see around an object. wow! cool.
 « Last Edit: November 27, 2008, 05:37:06 pm by amarMabbu » Logged
amarMabbu
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 « Embed this message Reply #21 on: November 27, 2008, 05:25:56 pm »

this is my eureka moment! i've got it to play, like the instructions read, i upgraded the JRE to the latest one.

just one word. AWESOME! actually thinking abt it, another word comes 2 mind too, PRICELESS.

this simulation shows elegantly, how the path of the meteors can be visualized.

mr. Hwang. i'm pushing the envelope here, but i'll try anyways. could u come up with a similar simulation for the fields around an electrically charged particle and a magnetic particle? ;-)

i won't ask 4 more, 4 now.
 « Last Edit: November 27, 2008, 05:37:48 pm by amarMabbu » Logged
Fu-Kwun Hwang
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 « Embed this message Reply #22 on: November 27, 2008, 09:03:21 pm »

Registed user can get files related to this applet for offline access.
Problem viewing java?Add http://www.phy.ntnu.edu.tw/ to exception site list
If java program did not show up, please download and install latest Java RUN TIME

For gravitation field, the potential energy is U(r)=-GMm/r (gravity field=-GMm/r2).
For electric field, the potential energy is U(r)=KQq/r (electric field=KQq/r2).

So the above gravity field simulation will be similar to one free charge moving around another fixed (and oppositive)charge.
If two charge are the same polarity, they will repel each other instead of attract with each other.
I will try to create another simulation which two particle moving around their center of mass.

But I do not understand what do you mean about "magnetic particle"?

I hope the following simulation is what you want.
You can change the position and velovity for each change particle, however, under the constraint that:
The center of mass is at x=0,y=0 and the velocity for center of mass is zero. Otherwise, both particles will move out the simualtion region gradually.

Remember: particle actually moving in the x-y horizontal plane. The trajectory in the simulation is not the real trajectory for those particle. Projection of their trajectory to x-y plane is the real trajectory. The change in the z-coordinate in the simulation is used to show how the potential energy change (i.e. Z is the potential energy)

Registed user can get files related to this applet for offline access.
Problem viewing java?Add http://www.phy.ntnu.edu.tw/ to exception site list
If java program did not show up, please download and install latest Java RUN TIME
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amarMabbu
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 « Embed this message Reply #23 on: December 01, 2008, 04:06:28 pm »

i've been caught up with what's happening in Bombay. it will take some time 4 me to go over ur post/Q and reply.

i appreciate ur wonderful work.
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cpsclicker
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 « Embed this message Reply #24 on: September 03, 2012, 10:54:18 am » posted from:Manila,Manila,Philippines

Thanks a lot for the help.. It answered my questions..
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Discovery consists of seeing what everybody has seen and thinking what nobody has thought. ..."Albert von Szent-Gyorgyi(1893-1986, 1937 Nobel Prize for Medicine, Lived to 93)"
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