Maybe this is a stupid question, but I dont understand what force is driving photons in light beams to go up and down, making a sine wave. How often in which it oscillates determines the frequency yeah, but why does it do that in the first place? And why is it that when light is emitted, instead of scattering like individual particles, the photons stay in a line. Like there’s a force that is keeping them in a straight line, and theres a force causing them to oscillate. Maybe they arent forces, but I just don’t get it.
In: Physics
Consider a [Mass-Spring System](https://thumbs.gfycat.com/GaseousPoliticalAlaskajingle-size_restricted.gif)
It oscillates back and forth. How and why? Gravity and the such right? But lets not worry about what makes it move and instead consider the energy balance.
At the peak, we have maximum potential energy, zero kinetic. In the middle we have maximum kinetic, zero potential. And at the bottom again max potential, zero kinetic.
Lets try to [Graph This](https://upload.wikimedia.org/wikipedia/commons/thumb/e/ea/Simple_Harmonic_Motion_Orbit.gif/260px-Simple_Harmonic_Motion_Orbit.gif)
We see the position as it moves up and down on the Y axis, and we see the speed/velocity on the X axis. Notice that at max position (top or bottom) we have no speed, and at max speed we are at position zero (origin).
What the circle illustrates is the conservation of energy, and the X and Y coordinates indicate how that energy is being distributed between potential and kinetic energy.
Light behaves in the sane manner. Electrostatic energy is just a form of potential energy, and magnetic energy is just the kinetic form of electrostatic energy.
If youve seen maxwells equations, this should make sense. Why is there no such thing as a magnetic monopole? Because magnetism can only exist as electrons *in motion*.
So to answer your question, light oscillates because it is exchanging a set amount of energy between potential and kinetic energies in exactly the same way a mass-spring system does.
[Bonus Gif](https://i.redd.it/4tt857no9xr01.gif) heres how light really travels, and why people say it possesses “wave-particle duality”. Also shows what Eulers identity actually means
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