Question: I was watching a documentary recently and there was an experiment where 2 electrons were shot through 2 separate metal slits. When the electrons were being observed, they behaved like 'normal' electrons and went through the 2 slits. When only observed by a camera and not by person, the electrons acted like waves. However, when the observer shut his eyes as the elecrons were shot, then opened them again, the electrons behaved like waves until the moment the observers opened their eyes, and turned into 'normal' electrons again, as if they had been shot through the 2 separates slits. What is your way of explaining this?

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  1. Good question. I don’t think it is quite as you have explained it (although you are close), The act of trying to measure in any manner “which slit” the electron goes through causes its wavefunction to “collapse” and go through one or the other – and this destroys interference. This is because the wave function of the electron has to go through *both* slits in order for an interference pattern to be detected.

    It turns out that this question is still the topic of research – and an experiment on this was rated as the number one breakthrough in physics in 2011!

    I have met the lead researcher a couple of times – he actually spent a few months working at the University of Queensland with a colleague of mine.