Why reality changes when you look at it | The Double Slit Experiment | with Jim Al-Khalili
Why Physics Stack Exchange recommends it
Physics Stack Exchange users cite it as the common popular explanation of the double slit experiment, then ask follow-up questions about how the observation and the detector in it actually work.
Recommended by 0 people across 0 different months, 2020 to 2022.
What it is
Jim Al-Khalili of the Royal Institution walks through the double slit experiment in a short lecture clip, showing how electrons build up an interference pattern and how that pattern disappears when a detector watches which slit they use. He frames it as the central mystery of quantum mechanics and a standard demonstration of wave-particle duality.
What people said
Cites Tian · 2020-04 · Physics Stack Exchange · on “Waching particles go through the double slit?”
Sorry in case this is a duplicate, I haven't studied physics or maths, and I can't find answers anywhere. The double-slit experiments are frequently explained online like the one here: [this video] The explanation says: Shoot particle through two-slit: get interference (wave behavior). Shoot particle one by one through two-slit: still get interference (wave behavior). Shoot particle one by one through two-slit AND watch them: no interference (particle behavior). Shoot particle one by one through two-slit AND PRETEND to watch them but switch off the camera: get interference (wave behavior). My main question is (ref. 3, 4): How can you WATCH which slit the particle goes through, surely you need pho
Cites Tristan · 2021-10 · Physics Stack Exchange · on “How does the photon detector in this video work?”
In this video: [this video] How does this photon detector at 6:58 work, mechanically speaking? Is this basically just like a camera, that beeps when it is hit by light? But how can it trace the path of the photon if the photon does not hit it and instead hits the screen - does it register electric radiation, or EM radiation, emitted by the photon, and thus can track a photon from the "side"? At 8:03 he notes that the result changes if you unplug the detector. I am assuming that this is explained by some sort of observer effect, but what is that observer effect exactly - what is changing physically when you unplug the detector? Is the detector just like a camera or does it, itself, emit radiation?
Cites OdinOblivion · 2022-08 · Physics Stack Exchange · on “Particle like nature of electron in single-slit experiment”
For explaining the double slit experiment, many such as Jim Al Khalili ( [this video] ) start with an example of having one slit - the pattern on the screen is that which you expect from particle-like behaviour. When there are two slits the probability waves of two electrons interfere to create an interference pattern arising from their wave-like behaviour. Since particle like behaviour when observed is still a wave, just concentrated at one point probabilistically, since the electron is unobserved, why does a single-slit experiment not also show wave-like behaviour and spread out (like light would)?