Some Key Ideas in Quantum Physics. References. R. P. Feynman, et al., The Feynman Lectures on Physics , v. III (Addison Wesley, 1970) A. Hobson, Physics: Concepts and Connections, 4 th ed. (Prentice Hall, 2006). Nano is (typically) Quantum Mechanical.
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Some Key Ideas in Quantum Physics
N1
N2
N12
I1
I2
I12
Not I1 + I2!
A
Light source
Werner Heisenberg
We have to remember that what
we observe is not nature in itself,
but nature exposed to our method
of questioning. – Heisenberg
Max Born
Erwin Schrödinger
A philosopher once said “It is necessary for
the very existence of science that the same
conditions always produce the same results.”
Well, they don’t!
– Richard Feynman
Faster
Slower
(Think of this as the size of the region in space where the particle is likely to be found.)
If we measure the speed we will get a range of possible results, with a variation of about s
where h is a fundamental constant of nature (“Planck’s constant”) and m is the mass of the particle
Speed
Speed
s
Position
Position
x
Speed
Speed
s
s
Position
Position
x
x
Rectangle must
have the same
area as before
Baseball RoP (not to scale!!)
Electron RoP
Proton RoP
Area of the rectangle is reduced if m is large!
Arrange these objects in order, beginning with the object having the largest “realm of possibilities” and ending with the one having the smallest: proton; glucose molecule C6H12O6; helium atom; baseball; electron; grain of dust; water molecule; automobile.
Some physicists would prefer to come back to the idea of an objective real world whose smallest parts exist independently in the same sense as stones or trees exist independently of whether we observe them. This however is impossible… Materialism rested on the illusion that the direct “actuality” of the world around us can be extrapolated into the atomic range. This extrapolation, however, is not possible – atoms are not things. [emphasis added]
– Werner Heisenberg
E = hf
“Classically
forbidden”
region
(KE would
be < 0)
Maximum height
(KE = 0)
Too slow!