Wave or particle ?

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Wave or particle ?
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Brief History Lets go back to 100 years ago ..
1684 Isaac Newton, Principa 1768 Stream engine
was invented.. 1781 I. Kant, Critique of Pure
Reason 1783 American independence revolution 1789
French revolution 1831 Electric engine was
invented Science is almost ended in the Newton
physics and Maxwell equations. All others are
just details. From human side, they believe
that human beings are good enough to protect
this world and themselves. However, the first
was broken by the discovery of quantum physics in
1905, while the second hope was broken by World
War I in 1914.
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Example I Periodic table
Order ?
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Example II Atom structure
How can atom be stable ?
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Example III Light spectrum
What these lines mean ?
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Max. electron energy
Photoelectric effect
What shall we expect ?
Intensity
Max. electron energy
Frquency
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Max. electron energy
Photoelectric effect
Experimental fact
Intensity
Max. electron energy
Frquency
Why ?
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Max. electron energy
Max. electron energy
Intensity
Intensity
Max. electron energy
Max. electron energy
Frquency
Frquency
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Conceptual questions.
What is the meaning of frequency, waveelngth
for a single photon ? What is the meaning of
quantized energy for a light wave ? How could
we understand the interference effects between
two light sources by photons ?
Is light a wave or a particle ?
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Double slit experiment for electrons
What shall we expect ?

• A particle cannot pass two holes at the same time
• It must pass through one of them
• ProbabilityP1P2

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What is this wavelength about ?
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Double slit experiment for electrons
The experimental results

• We find interference pattern for particles !
• An Electron must have to pass both hole at the
  same time ?

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If we want to measure it..
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We find a very surprising result.
Both light and massive particles are not like
what we expect in the ordinary situation.
Their properties cannot be simply understood by
our common sense in the ordinary world.
We need to do the experiment to measure their
properties before we could say about them.
But measurement can changes the results
dramatically . Is there something wrong ?
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Basic concept of Quantum mechanics
1. For an EM wave, we have
2. For a massive particle, we have
5. One could not know anything (but probability)
about a single event
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But not only we do not like it.
A. Einstein God does not play dice with the
universe.
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Gradually we used to it.
R.P. Feynman I think it is fair to say that
no on really understand quantum mechanics. We
just know how to calculate it.
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Quantum tunneling
STM
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STM image
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Matter wave to understand this world..
Standing wave gives discrete energy level !
Ehv makes the discrete energy level to be
observed by discrete light spectroum.
Pauli exclusion principle then explains the
preriodic table !
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Visible quantum world..
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Quantum world is much more dramatic than what
people could image in ordinary life !
What is more surprising is we human beings can
understand this strange world ?!