If you were to shine a flashlight onto a blank wall, you may be surprised to see that the beam makes a series of rings wherever it lands. That’s a result of what’s called interference—the waves of light crashing into each other more or less in sync. If the waves are synched up, you have constructive interference, and you get a brighter signal. If the waves don’t line up, you have destructive interference, and you get a darker signal. If the waves are perfectly ‘opposite,’ the destructive interference is at its most extreme, and you get no signal at all.
Light is the easiest example, but it’s not the only thing that experiences interference. Interestingly, electrons can interfere as well if they have perfectly different energies. This can lead to the existence of ‘dark electrons’—electrons in ‘dark states’ that are you can’t see with a spectroscope.
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