Okay, so I know that a wavelength is a distance of crest and a trough added together which makes a whole wave, but what is it in the real sense? Like in the case of sound I know when we say "frequency" we mean how fast the air molecules are going away from their mean positions and coming back which is how fast they are vibrating basically. And in the case of light I assume it would be how fast a charged particle is vibrating to produce electric and magnetic fields.
But what is wavelength in sense of the electric/ magnetic fields. Like if I say there are two waves of light with a long wavelength and a short wavelength. I can imagine it in my mind that the distance between the crest and trough of the magnetic/eletric field for the longer wave is greater than for the short wave. But what does it mean practically? Does it mean that the electric fields (and magnetic) are created for the longer distance?
Another confusion this creates in my mind is that what exactly is a trough for electric (magnetic) field? Does it mean a field in the opposite direction? Lets say theres an electron vibrating with changing velocities. It is creating all around a changing electric (and magnetic) field around it. But how do we connect this with the electric (and magnetic) field in the wave image of light?