I see lots of drawings illustrating amplitude, frequency, etc using a sine wave to represent an EM wave, but why are they drawn like this? What do the crests and troughs mean/what values do they represent? And what do these waves look like in real life?
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The electric and magnetic field are at 90 degrees to each other and 90 degrees to both of them is the direction of propagation (the poynting vector, which is also the energy flux). Think of the edge of a cube, you have three edges at 90 degrees to one another.
Now the amplitude of the wave is the maximum strength of the electric and magnetic fields. The frequency is how fast it goes through that cyclic change.
To answer *How does it actually look*? It’s just a bunch of photons traveling through space having that variation described – the photon travels in a straight line (if it doesn’t get affected in it’s path).
So when drawings show the amplitude and frequency, they’re showing the electric and magnetic field strength (amplitude) varying at a certain cyclic rate (frequency).
But humans can’t see radio waves because their wavelengths are about 1mm to up to 10,000 km so they have no *color* for us to see them.
Radio waves are part of the electromagnetic spectrum, and we can only see a part of this spectrum. The part we can see is called visible light – which is 700 nm (red) to 400 nm (violet) wavelengths.
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