L02 Double Slit Experiment

Double-slit Experiment
Lagniappe: Double
Slit Experiment
Who put the quantum in mechanics?
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Thank you, RPF.
Some of the graphics are from Wikipedia
and other web sources.
Double-slit Experiment
This discussion is heavily based on the
material in Chapter 37 of Volume I of The
Feynman Lectures on Physics.
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detector
Double-slit Experiment
Double-slit Geometry
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baffle
backstop
Poorly-aimed Indestructible
Bullets
detector
𝑃12
Double-slit Experiment
𝑃1
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𝑃2
baffle
backstop
Water Waves
detector
𝑃12
Double-slit Experiment
𝑃1
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𝑃2
baffle
backstop
Double-slit Experiment
Another View
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Double-slit Experiment
And Yet More Water Waves
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Results So Far
β€’ For water waves, it’s all wiggly
𝑃12 β‰  𝑃1 + 𝑃2
Double-slit Experiment
β€’ For bullets, it’s simple
𝑃12 = 𝑃1 + 𝑃2
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Try Electrons
detector
Double-slit Experiment
detector gives discrete
clicks when electrons
arrive
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baffle
backstop
Measure Electrons Probabilities
detector
𝑃12
Double-slit Experiment
𝑃1
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𝑃2
baffle
backstop
Double-slit Experiment
An Actual Electron Experiment
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Spy On The Electrons
detector
𝑃12
Double-slit Experiment
𝑃1
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𝑃2
baffle
backstop
What To Do?
β€’ Turn down the lamp’s brightness.
β€’ Increase the lamp’s wavelength.
β€’ Lose resolution.
β€’ Get a wave result when resolution is too poor to
identify hole.
Double-slit Experiment
β€’ Get a mixture of bullet and wave distributions
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What Does It Mean?
β€’ We cannot say the electron went through one
hole or the other.
β€’ If we disturb the electrons too much we
get particle-like (bullet) results.
Double-slit Experiment
β€’ If we don’t disturb the electrons we get
wave-like results.
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We don’t know.
β€’ We can predict the odds of a particular
outcome.
β€’ The Uncertainty Principle prevents us
from measuring the β€œreal” behavior of the
electrons.
β€’ We cannot identify a deeper, underlying
theory.
Double-slit Experiment
What’s Underneath It All.
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