Particles and Waves

Light behaves as both a particle and a wave. This is a core part of the standard model of physics and is interesting for a number of reasons. Two things in particular are on my mind of late.

First, I spent a long time trying to wrap my head around how light can be both at the same time. If it behaves as both, it must somehow be both. I've seen a number of people hit that wall and just give up on ever understanding physics or anything quantum.

But that doesn't have to be. Light is neither a particle, nor a wave, nor a duality. It is something else. Light is its own, unique thing. It happens to sometimes behave like our model of a particle. And at other times it behaves like our model of a wave. Thinking it's somehow both is getting hung up on the labels of our models. The fact that light acts kind of like one model and kind of like another just means that neither model by itself is correct.

And that means that neither label is correct, either. Light is light. The fact that it doesn't fit under the intuitive sounding labels Particle or Wave is irrelevant. Even if it behaves like them sometimes. Especially if it behaves like both at some time or another. Light is light, and we need to think of it as its own thing.

I can't recall who said that first... perhaps Hawking? Regardless, when I read that the apparent paradox vanished and my thinking became a lot clearer. Hopefully more people can come to understand that and move past this particular hurdle to their understanding of physics.

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Second, I'm fascinated by the double slit experiment that so aptly shows that the nature of light is neither a particle nor a wave. For those not familiar with the experiment, google it up. It's amazing.

I recently read Programming The Universe, in which the author discusses how the photon could interact with itself as it passes through both slits to form the interference pattern we see even with single photons shot through the apparatus. What I'm curious about, and haven't been able to find in an admittedly cursory glance around the web, is how far apart the two slits can be to still get the effect.

I'm thinking of an electron's cloud/orbit around the nucleus of an atom - it's not really an orbit, the cloud is more of a probability volume, where the electron is very likely to be at a given time. If a photo has a similar probability volume, it seems likely that the slits couldn't be any further apart than the diameter of the probability volume. After a certain distance apart, the two slits essentially become two separate, individual slits.

The question is - does a photon behave like an electron, IE: does it have a probability distribution for it's location at any given time? And if so, is that related to the wave length or amplitude of the wave, or is it a separate variable? And if so, what is it called?