1 / 8

QUANTUM MECHANICS Probability & Uncertainty

QUANTUM MECHANICS Probability & Uncertainty. Probability Uncertainty Double-slit photons. P( S ) = Probability of getting sum S. Probability. EXPERIMENT. THEORY. # times S occurs # all throws. # ways to get S # all possible outcomes.

ervin
Download Presentation

QUANTUM MECHANICS Probability & Uncertainty

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. QUANTUM MECHANICS Probability & Uncertainty • Probability • Uncertainty • Double-slit photons

  2. P(S) = Probability of getting sum S Probability EXPERIMENT THEORY # times S occurs # all throws # ways to get S # all possible outcomes Experiment approaches Theory after more & more throws, but always fluctuates.

  3. Wave represents probability of particle detection at a particular place and time (Max Born) Quantum Mechanics Big Idea Solves wave-particle duality paradox Wave = THEORY Particle = EXPERIMENT (compare to dice) Quantum Waves: P = h2 Wave Height h Intensity => Probability P Double Slits – Location of bright bands has high probability of photon hits

  4. New kind of scientific model Probability : Cannot predict result of anyone detection Detection : No objective reality before measurement U C N E R T A Y I N T • Classical physics deterministic • Can predict future position & speed • with arbitrary precision • Quantum physics probabilistic • Can predict only probability of observing certain • future speed or position

  5. X ? How is position of an object detected? Observe (e.g. with light) Increasing certainty of position X, decreases certainty of momentum P (momentum = mass times velocity ) A photon bounces off (detection) Object gets an uncertain `kick’ (changes velocity) Observe

  6. Measure X ± ΔX Measure P ± ΔP QM says can make either ΔX or ΔP arbitrarily small (not zero) by better experiment BUT… there is a theoretical limit on both simultaneously: Heisenberg Uncertainty Principle ΔX timesΔP is always more than h h = Planck constant (very small) • Smaller ΔX implies largerΔP ….and vice versa • Limit only noticeable at atomic sizes • Uncertainty Principle applies to everything, including us

  7. Revisit….Double slit photons: Quantum mechanics -> wave represents probability of particle detection -> measurement uncertainty Paradox ? Interference pattern result of two slits, but each particle must go through only one slit (surely?) QM : before detection, cannot say which slit particle went through (no definite path) Act of looking alters the wave.. If detect which slit each particle passes through -> no interference pattern

More Related