|>> || >>79081 |
OK. I'll finally try to follow up. Quickly.
In the last post, I brought us up to the point where physicists saw that light is emitted in packets called 'quanta' at the time. They knew that because of theoretical work following the 'ultraviolet catastrophe'.
But they also knew light acts as a wave, since a single wavelength passing through two slits produces a diffraction pattern (like water waves going through small slits). This is Young's double slit experiement, and was actually an early 19th century experiment (predating most of the experiments I'm talking about here).
They also knew light is a wave because Maxwell's Equations can be used to describe light as an electromagnetic wave very accurately.
But, unlike waves, light didn't appear to travel through any medium. Sound travels through air, ocean waves through water, 'guitar waves' on taught strings, etc. They called the theoretical media that light uses "ether", but attempts to prove its existence failed (the michelson morley experiement).
They also realized that, in many cases, light spectra weren't smooth and continuous. They had very sharp, unexpected lines.
Also at this time, Einstein described the photoelectric effect, where light could be absorbed in quanta
In other words, there were a bunch of experiements and theoretical models that "proved" light was a wave. And there were a bunch of experiements and theoretical models "proving" that light is a particle. I'm not sure if the following is how it developed historically, but I'm trying to mirror how it's typically taught progressively. I might be getting the exact order and technology used at the time wrong.
Now all that brings us to the more advance two-slit experiments. At some point, some idiot decided to try the two slit experiment with electrons. We *know* electrons are particles. There were detectors that can detect a single electron. The mass of the electron was known. It's a fucking particle. But when shot through two slits with a detector on the other side, the detector see a wave-like pattern.
Same with neutrons. WTF? Protons and electrons are particles for sure. They have mass. They make up virtually our entire world. So this was a shocking result to see them behave as waves.
When a wave passes through two slits, mathematically modelling the pattern is produces is fairly simple. One of the most important variables in modelling the wave is the wavelength (especially in relation to the size of the slit, the slit spacing, etc.). Well, it turns out these electron and proton waves could be modeled just the same.
In these mathematicals models, the wavelength is proportional to the mass (and velocity) of the particle. This is called the de broglie wavelength. Basically, the more momentum something has (the faster it's going, or the more massive it is), the smaller its apparent wavelength is in this experiment (and others). https://en.wikipedia.org/wiki/Matter_wave
The de Broglie wavelength is the first 'weird' equation you'll see in a quantum physics textbook, because it shows how there's a smooth transition from the quantum weirdness of particles to more human sized objects. The more mass or velocity something has, the smaller this wavelength gets. The smaller the wavelength gets, the less you'll see this apparent wave behavior. So an electron is very wave-like. A proton, slightly less so. An atom (say, He) could see some wave-y stuff. A molecule, too.. although it's getting less likely. When you plug in the numbers for something like a bullet, or a tennis ball, you'll see that the wavelength is so small, it's meaningless. But there is that transition.
Hopefully that wasn't too rambly.