what is the original equasion for light travel?

Answer 1

The equation comes from that a change in an electric field causes a change in a magnetic field, which in turn causes a change in the electric field at a small distance away. The process repeats and you get a traveling disturbance which people generally conceptualize as waves, much like the ones you'd get by jerking a piece of rope that's attached to something and sending a wave down it.

In the rope case one bit of rope causes the bit of rope right next to it to move in a certain way. The in turn causes the bit of rope next to that one to move in a certain way and so on. That's probably a lot easier to visualize and is the same basic idea of what the last paragraph said.

The website the one dude gave you, has all the equations you need to derive the wave equation for light, but I don't think it actually gives it to you. Anyway the equation is

(1/c^2) d^2 E/dt^2 - d^2 E / dx^2 = 0

Its a differential equation and that c in there is the speed of light. E refers to the electric field in some fixed direction. That equation just says in mathematical symbols what I said in words in the first paragraph if all this is a little over your head. It was this equation which was the first to suggest the existence of Electro-Magnetic waves (light) and their speed.

You still might be wondering where c really comes from though. It comes from Maxwell's equations (which is where the wave equation came from), which in turn came from Gauss's and Faraday's laws. c is a result of a combining other previous physical constants that were necessary for formulating those last two laws I mentioned and those constants came from experimental observation.

Answer 2

It is called wave EQUATION

http://en.wikipedia.org/wiki/Wave_equation

Since it is an elecromagnetic wave a knowledge of Maxwell's equations is suggested
http://hyperphysics.phy-astr.gsu.edu/HBASE/electric/maxeq.html

And we should not forget other raspects of light as well

E=hf

Or do you mean what are the equations for travel at the speed of light. Then using Lorenz factor we have equations for relativistic mass (m’), length (L’) and time (t’).

m'=m/SQRT(1-(v/c)^2)
L’=L/ SQRT(1-(v/c)^2)
t’=t/ SQRT(1-(v/c)^2)
where v=speed of the object and c=speed of ligt.

Ref http://en.wikipedia.org/wiki/Special_Relativity

Answer 3

In geometrical optics, it follows Fermat's principle:

The actual path between two points taken by a beam of light is the one which is traversed in the least time.

So d(P)/dt=0

With P the optical path length: Sum of n (index) * d (distance)

Answer 4

distance = speed of light x time
distance = 300 Mm/s x time
(M = mega = million)

Answer 5

Do you know it , you misspelled equation