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Physics

Wave-Particle Duality: The Double-Slit Experiment

Quick fact

When the double-slit experiment is performed with electrons and a detector is turned on to see which slit each electron goes through, the interference pattern disappears and only two bands remain.

Why this is interesting

Imagine firing tiny particles at a wall with two slits. You'd expect to see two bands, right? But when you don't look, they paint a pattern of many bands—as if each particle went through both slits at once. What's going on?