what exactly is wave (e.g. wifi, radio) and how does it travel in the physical world?

Question

I really can’t grasp the concept of waves. I can imagine it a bit for sound waves: a speaker has a surface that pushes air, and the moving air eventually pushes the membrane in our ears.

But I’m confused about wifi etc. What exactly is the thing that physically travels? Is it air or something else? Does it physically move in a wavy pattern?

Edit: thanks for all the answers! But damn I’m overwhelmed. It’s gonna take me days to read and fully understand the answers. But thanks!

In: 87

Answer 1

Waves are an oscillation in a medium. Any individual piece of the medium only gets slightly disturbed, but the wave as a whole moves on. Like shaking a rope back and forth, that’s technically cresting a wave, but the wave it moving away from where you’re shaking while the rope just moves up and down, not away.

Electromagnetic radiation (light, radio/wifi, infrared, UV, x-rays, etc) are unique in that they don’t require a medium. Like the wave on the rope, the rope is a medium, for a sound wave, the air is the medium. Instead it’s just electric and magnetic oscillations, basically the constantly changing electric field causes a magnetic field, and since that’s constantly changing it creates an electric field, and it just goes on and on until it hits something, and those interactions take place at the speed of light, so the wave as a whole moves at the speed of light.

We can create and absorb light because we are made of atoms, which have protons and electrons, which have charge, and therefore have an electric field. If they move in the right way, they can move in such a way that creates the electric field will will go on top a magnetic field that will make a new electric field and so on and so forth. (Note: it’s not oscillating between being electric and magnetic, both are happening at the same time, one can’t exist without the other)

Microwave ovens work on basically the opposite of this. They create waves that have just the right properties such that when it hits a water molecule, it will get absorbed and vibrate the molecule. The molecule vibrates with the same frequency as the wave so when the next one comes along it vibrates the molecule even more. This intensified vibration is the heat.