Are EM waves really waves or straight lines?

[ChrisHansen2Legit2Quit]

If you hook up a scope to a microphone and speak into it, you will begin to see a voltage fluctuation on the scope; a sine wave.

But when you look at leads coming off the microphone, you dont actually see electricity waving up and down with respect to the lead.

So whats up with this wave on the scope? Well, its just measuring voltage over time.



Am i supposed to think of propagating EM waves like this or is okay for me to take it literal (ie the really travel as waves. Not in straight lines)

Thank you!

 

[albbg]

An electromagnetic waves, that is electric and magnetic fileds, propagate in vaccum space as straight lines, but both electric and magnetic fields are varying over time.

Let suppose transmitting a sinewave at an angular frequency "w", then observing the beahaviour of the electric (or magnetic) field in a point P, in the space, we will see something proportional to sin(w*t) if we move far away from the source to a point P1 (motion along the line connecting the source with P) we will see the same behaviour as in P but attenuated and delayed by the time the wave needs to travel from P to P1. This time delay can be converted into phase delay "phi" depending from the frequency of the signal, so we can write sin(w*t+phi).

 

[cannibol_90]

As albbg said, Electromagnetic waves are time varying with electric and magnetic fields being perpendicular to each other. When a source expands and contracts absolutely consistently (unfound in nature) it is said to be moving in simple harmonic motion. The wave it produces is known as a sine wave.

Sine wave is the basic to everything. A periodic function can be taken as the superposition(sum) of infinite number of sine waves, which forms Fourier Series.

Maxwell said that in addition to conduction current which flows in a conductor, there is displacement current that can flow through air, free space, dielectric(capacitor) et al. Without displacement current wireless communication would not exist today.

So, EM waves has both conduction as well as displacement current that continuously varies and yes it travels in a straight line just like light does.