Is light electromagnetic waves or quantumn particle waves?

Question

Is light electromagnetic waves or quantum physical particle waves. Or are they the same?

Note: My question is specifically how electromagnetism plays into the quantum physics and the double slit experiment.

Answer 1

Physicists tend to just use whichever model fits the behavior they're studying at the moment. The most accurate description of the behavior of light is: light behaves like light. That's not a very useful, but it is not wrong.

Light is both particles and EM waves; it just depends on what you'd like to do with it, and whichever model most accurately describes reality. If it helps your understanding more to treat it like a wave, then do so. If the wave model does not make sense, try the particle model.

Quantum Mechanics is kind of brain-stretching sometimes, and you may want to look at a possible duplicate here.

Answer 2

Light is light. It isn't a particle and it isn't a wave; it is another sort of phenomenon that was mostly misunderstood until the last several decades.

There are a lot of things about light that are like classical waves. If you have a lot of light you can talk about it as oscillations in a field, the way that water waves are oscillations of the water-air interface. Like classical waves, you can set up light waves to interfere with each other.

There are a lot of things about light that are like classical particles. The energy and momentum of light come in lumps, like the energy and momentum of a bullet. If you are sufficiently careful you can emit and absorb these lumps one at a time.

But there are lots of situations where neither the wave model nor the particle model of light is very useful. Scientists and the science writers who follow them try to help us wrap our poor monkey brains around the difference by sticking to these analogies until they are no good any more, leading to statements like "light is a wave sometimes and a particle at other times." This is a useful way to conceptualize a problem, but it sounds like a mysterious swindle, like the first time your older sister told you that her grubby dime was just as good as your ten shiny pennies.

Fortunately for us, it turns out that there are lots of things that are like light. In fact, so far as we've found, everything is like light: energy and momentum come in lumps, but if you are careful you can make the lumps interfere with each other, whether it's a lump of light or a lump of electron or a lump of molecule or a lump of sound. If it turns out that dark matter or dark energy are not like light, that will be very interesting.