superfast light


by rshreyas
Tags: light, superfast
rshreyas
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Sep13-13, 06:46 AM
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all objects travel at a speed .when we come to light , the speed is approximately 3 * 108 . i am confused about how can it travel with such a speed . i have surfed in the internet but it only says that it is not yet proved . i wish to know the answer . this could help me to study optics more perfectly . did Einstein prove in the theory of relativity.
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SteamKing
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Sep13-13, 06:58 AM
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The speed of light has been measured numerous times and the speed measured is approx. 3*10^8 m/s. The speed of light in a vacuum is a fundamental constant in physics. The rest of your ramble makes no sense.
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Sep13-13, 07:14 AM
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Quote Quote by SteamKing View Post
The speed of light has been measured numerous times and the speed measured is approx. 3*10^8 m/s. The speed of light in a vacuum is a fundamental constant in physics. The rest of your ramble makes no sense.
i agree to it .but, there should be a reason for light to travel in such a speed . you just gave me a reason which i know.

DaleSpam
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Sep13-13, 07:19 AM
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superfast light


Quote Quote by rshreyas View Post
the speed is approximately 3 * 108 . i am confused about how can it travel with such a speed
Classically, all electromagnetic phenomena follow Maxwell's equations:
http://en.wikipedia.org/wiki/Maxwell's_equations
http://hyperphysics.phy-astr.gsu.edu.../maxeq.html#c3

The speed of light falls naturally out of Maxwell's equations. There is simply no other speed at which it can travel through vacuum and still obey Maxwell's equations.
Claude Bile
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Sep13-13, 07:20 AM
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It was Maxwell who demonstrated that EM waves travel at the speed of light, which can be expressed as a combination of other fundamental constants associated with electromagnetism (Einstein demonstrated that the speed of light is a universal speed limit).

We know the value of these fundamental constants from observation - by determining the force between two charges etc.

Claude.

Edit: beaten by Dale!
HallsofIvy
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Sep13-13, 07:26 AM
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Quote Quote by rshreyas View Post
all objects travel at a speed .
This is not true- at least not in the since that you mean when talking about light. A specific automobile, at a specific time, is traveling "at a speed". Different automobiles, or that same automobile at different times, may travel at different speeds. But all light, at all times, in vacuum, travels at "c".

when we come to light , the speed is approximately 3 * 108 . i am confused about how can it travel with such a speed . i have surfed in the internet but it only says that it is not yet proved . i wish to know the answer . this could help me to study optics more perfectly . did Einstein prove in the theory of relativity.
dauto
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Sep13-13, 07:48 AM
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I confused about what you're confused about. What is the question? Light travels at a certain speed. That speed has been measured to be about 3 * 10^8 m/s. What don't you understand?
jtbell
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Sep13-13, 09:46 AM
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From the FAQ section of our relativity forum:

Why does c have a particular value, and can it change?
Nugatory
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Sep13-13, 09:58 AM
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Quote Quote by quawa99 View Post
This is just an intutive idea:you know light is produced from various sources like light bulbs, candles etc. Basically light is produced due to de-exitation of the electrons in the material i.e the heated filament in a bulb loses that heat energy in the from of light.Now light consists of particles called photons which have a zero mass so even if we give very little energy to it light can go very fast.imagine you hit a bowling ball with a bat and a cricket ball with the same force ,you can notice that the cricket ball will go very fast in a similar way light has zero mass so if u hit a photon with the same force it will go superfast .(This is not a perfect answer and I know it may not be correct to say to hit a photon with a bat but like i said i just wanted to give an intutive idea)
Subatomic particles in general and photons in particular do not behave like cricket balls or bowling balls; the word "particle" in in this context means something very different from the standard non-technical usage.

If you want to understand the behavior of light, your best bet may be to try to forget that you ever heard the word "photon", and work your way through the classical model of light as an electromagnetic wave instead. You can go back to thinking about photons when you're ready to move beyond classical physics and take on quantum mechanics.
ZapperZ
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Sep13-13, 12:01 PM
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Quote Quote by quawa99 View Post
This is just an intutive idea:you know light is produced from various sources like light bulbs, candles etc. Basically light is produced due to de-exitation of the electrons in the material i.e the heated filament in a bulb loses that heat energy in the from of light.Now light consists of particles called photons which have a zero mass so even if we give very little energy to it light can go very fast.imagine you hit a bowling ball with a bat and a cricket ball with the same force ,you can notice that the cricket ball will go very fast in a similar way light has zero mass so if u hit a photon with the same force it will go superfast .(This is not a perfect answer and I know it may not be correct to say to hit a photon with a bat but like i said i just wanted to give an intutive idea)
There is something misleading here. It gives the impression the ALL light is produced by some "de excitation of electrons" which is incorrect. I can take a bunch of electrons, and jiggle it up and down, and voila! I have light! This crude description is how we get the EM radiation from synchrotron light sources, and how we generate radio waves and microwaves.

And the analogy with hitting a ball is very puzzling. This is because it requires the bat to impart energy and momentum (speed) to the object. This is not true with light since the photons are born at c.

Zz.


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