Acceleration speed of light.

[Eurox]

How does light accelerate? Obviously it must somehow. From when you turn a light on to reach your eyes it must get to its 'c' speed. Ive tried looking it up but all it seems to say is that because light doesnt have a mass it has magical 'properties' that make it start from that speed, or change from one speed in a medium to another instantaneously. Can anyone help?

[CT]

That's about right. A photon of light is emitted at the speed of light. Due to it's properties, 'c' is the only speed it can travel at.

[Eurox]

Well how does it do that? In order for it to reach that speed it must accelerate somehow.

[vikramdave1]

I have heard with frequent conversations with my teacher, that light can be trapped in a box of some kind. Bearing this in mind light trapped in a box may retard slightly or it may behave like a gas which exerts a pressure in the box!

(I am only predicting as a 16 year old physics student, Einstein once said science can have childlike fagility at times)

[vikramdave1]

light has to accelarate and decelarate otherwise the laws of physics would not make sense. ENERGY CANNOT BE MADE OR DESTROYED ( First law of thermodynamics). You would be suggesting that a photon would have infinite energy which would keep travelling forever.

[vikramdave1]

light does decelarate thats why we get refraction

[Eurox]

So were agreed? Does anyone have any idea what the speed of the acceleration or deceleration is from a standing start?

[fo3nix]

vikram: photons _can_ travel forever. they just can. they dont have mass. they're unlike anything that does have mass.

and no, it does not accelerate and decelerate with refraction. you are mixing up phase velocity and group velocity of waves.

[fo3nix]

btw ive just found this:

http://van.hep.uiuc.edu/van/qa/section/New_and_Exciting_ Physics/Quantum_Mechanics/20031118161159.htm

[Loosehead]

Light is emitted from suitably excited atoms at c, they have no mass and therefore no acceleration.

[boobesque]

as we all know speed increases mass. if photons had mass then the mass would be infinite at the speed of light, as would the mass of anything that reaches that speed. if photons had mass they would not be able to travel at the speed that they do. when eurox or vikramdave post a video of light travelling slower than 300,000km/s let me know.

[mibn2cweus]

light has to accelarate and decelarate otherwise the laws of physics would not make sense. ENERGY CANNOT BE MADE OR DESTROYED ( First law of thermodynamics). You would be suggesting that a photon would have infinite energy which would keep travelling forever.

Energy does not require more energy to be and do what energy does. Energy has an equivalence to mass but is an entirely differant state of existent without mass. It is in essence motion devoid of mass and has no alternative but to move at the speed of energy (light) until it is imparted into matter.