Essentials Flashcards
What is the double slit test?
If one slit is blocked off, each electron flies neatly through and delivers a single scintillation on the sensors behind.
But if both slits are open, each electron seems to pass through both slits at once, interfering with itself and landing at completely random and unpredictable points on the screen. A fuzzy interference pattern on the screen, just as a wave would make. How can an electron “know” in mid flight whether it will encounter one or two slits?
And if a detector is positioned behind one of the slits, then we only ever see electrons choosing one slit and the interference pattern is lost.
Disturbingly, our act of observing a particle seems to affect, in advance, what it will do and how it will appear to us.
What is “spooky action at a distance” and who first proved it?
Quantum particles spin both ways at once until observed, forcing the particle to “make up its mind” which way it is spinning. When two particles interact in an experiment, the second one “knows” which spin to adopt. But this would need some faster-than-light force.
Seemingly proven in a 1982 experiment run by Alain Aspect at the University of Paris measuring the polarisation of light particles.
No matter how great the distance between them might be, “a pair of entangled [particles] should be considered as a global, inseparable quantum system”.
Why is the connection between photons of light energy and the electrons in an atom so key?
An absorbed photon kicks an electron into a higher energy state (or “orbit”). An electron dropping from a higher state to a lower one will emit a photon. All the light we see around us is generated by photons kicked out of atoms by electrons dropping from higher to lower states. The forms of light we don’t see - infra-red, ultraviolet, x-rays and gamma rays - are created in the same way.
