Wave-particle duality and quantum measurement interactive

Looking at an electron changes it

The double-slit experiment reveals that measurement isn't passive observation—it's an interaction that fundamentally alters quantum behaviour. When you detect which slit an electron passes through, the interference stripes vanish and the hits spread into one smooth band. Turn off the detector and the stripes return, showing each electron somehow passes through both slits. Raise the detection strength and watch the stripes fade, and switch between Wave view and Particle view to see the same experiment two ways.

Double-slit detector
Wave behaviour intact
Detection strength determines which quantum behaviour emerges
Both slits — interference visible
Detection strength
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Wave view shows the electron as a wave. With the detector off, the wave goes through both slits and the two parts overlap on the screen: where crest meets crest you get a bright stripe, where crest meets trough a dark one. This is not ignorance about which slit it "really" went through: with no path on record there is no single path. Fire electrons one at a time, hours apart, and the stripes still build up, so each electron interferes with itself. Turn the detector up and the stripes lose contrast; only at full detection are they gone, leaving one smooth band.
Know This
The act of measurement fundamentally changes quantum behaviour—not because of clumsy equipment, but because observing particle properties like position destroys wave properties like interference.