medium of light

[tech by trade]

new to the forums, had a question and thought someone might have an answer. If I remember from high school physics, in order for a wave to occur it must pass through a medium i.e.. sound through air, waves through water. my question is what do light waves use as there medium as they can travel through the vacuum of space. thanks for your time.

[dextercioby]

They don't.WAVES NEED SOURCES.Incidentally,light waves do not need support medium...Who told u that waves need a medium (substance:matter) to propagate,was not referring to light.If he was,he was wrong.

Daniel.

[tech by trade]

when we were learning about waves in grade 11 physics, our teacher said that waves needed a medium to propagate. I guess this kind of answers my question, but if light does not need any type medium to propagate, then is light waves in the same sense as sound waves or waves in water?

[dextercioby]

Nope,it's a special type of wave.It's the kind of wave that propagates in vacuum...It's a transversal wave.

Daniel.

[tech by trade]

so, let me get this right. light has to be made up of particles in order for it to be a transversal wave. so would it be right to say that the wave of light itself is the medium?

[dextercioby]

Not necessarily.It's a coincidence that LIGHT is made up of photons which have ONLY transversal degrees of freedom.As for the secod part,let's call light LIGHT,okay...?It's not a medium for anything.

Daniel.

[tech by trade]

Okay, i wasn't thinking of light as a medium, i was thinking of the light as a wave in the same sense as my previous examples. i am just trying to make sense of how light can travel through a vacuum. I guess my question would be how does light travel if it does not need a medium to travel on.

[dextercioby]

At classical (macroscopical) level light is made up of magnetic & electric field.The existance & the propagation concepts are independent of the "environment",whether vacuum,or not.

Daniel.

[Crosson]

The answer to "how light waves travel" is "by electromagnetic induction". They don't call them electromagnetic waves for nothing, they are periodic oscillations in the electromagnetic field.

If somebody asks me "what is waving in a light wave?" I give them the unambiguous answer "It is an electromagnetic field".

[kevinalm]

tech by trade

First let me be clear that dextercioby is absolutely correct. But I think that for clarity it would be good for you to understand that the distinction dex is making is of major importance only in the realm of Relativity. In other words where you would swich from using Newtonian to Einsteinian physics. Most real world calculations treat light if it were a wave traveling through a medium. Conceptually, it is convenient to think of it that way _as long as you understand it is not actually true_.

[tech by trade]

thanks, its starting to make some sense. i think more research is needed on my part.