The wave and particle duality of light…

O.K. like I was so not ready for the above question the other night, where the concept of light and its dual nature came up. Looking back, I’m still having a hard time thinking about the best way to talk about it. Partly because I’m still not convinced that it’s one of those things that can be explained in a logical fashion. i.e. it just is – because of variety of different observations suggest that it can exist as either or, or both (depending on how you want to phrase the diction). Mind you, I say this as a geneticist, a science person as far removed as a physicist could possibly be.

Maybe this video can shed light on the strangeness of it all?

…or maybe not?

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David (@ng_dave) is Faculty at the Michael Smith Labs. His writing has appeared in places such as McSweeney's, The Walrus, and He plans on using Terry as another place to highlight the mostly science-y links he appreciates. In fact, if you liked this one, you might also like his main site generally - this can be found at

2 Responses to “The wave and particle duality of light…”

  1. josh

    hmm. I got an A+ in quantum mechanics and I don’t understand it at all. Dr. Unruh claimed that if anyone says they understand it they’rr full of shit. Dr. Unruh is sort of an important character. I’m not sure this is encouraging either.

    ok. So the odd thing is electrons have a property called ‘spin’. They are not actually spinning (maybe?) but this property behaves similar to the property of spinning for objects we can comprehend. One electron alone has a certain probability of spinning in either direction (say counter-clockwise or clockwise). And this probability fluctuates over time. When it goes through one of the two slits, its spin determines which one it goes through. But it’s spin is really neither one direction or the other but a probability of spinning in one direction. When it goes through (alone) it sort of goes through both slits with different probabilities and is able to interfere with itself.

    Even more oddly, when you measure the spin of an electron it has to return an answer that is plus or minus one. It is either rotating clockwise, or counter-clockwise. The act of measuring fixes the spin of the electron from an otherwise probabilistic state into a deterministic one. Once you do this, the electron has to completely go through one slit or the other and you see it acting as a particle.

    Any clearer? It’s not for me…


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