5th solvay conference, brussels, 23-29 october 1927
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5th Solvay Conference, Brussels, 23-29 October 1927 Back row: A Piccard, E Henriot, P Ehrenfest, D Durfee, Ed Herzen, Th De Donder, E Schroedinger - PowerPoint PPT PresentationTRANSCRIPT
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5th Solvay Conference, Brussels, 23-29 October 1927 Back row: A Piccard, E Henriot, P Ehrenfest, D Durfee, Ed Herzen, Th De Donder, E Schroedinger
E Verschaffelt, W Pauli, Waldo, W Heisenberg, R H Fowler, L Brillouin.Middle Row: P Debye, M Knudsen, W L Bragg, H A Kramers, P A M Dirac, A H Compton,
L de Broglie, M Born, N Bohr.Front Row: I Langmuir, M Planck, Mme Curie, H A Lorentz, A Einstein, P Langevin, Ch E Guye,
C T R Wilson, O W Richardson.
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Postulates of Quantum Mechanics
Every physically-realizable system is described by a state function ψ that contains all accessible physical information about the system in that state
The probability of finding a system within the volume dv at time t is equal to |ψ|2dv
Every observable is represented by an operator which is used to obtain information about the observable from the state function
The time evolution of a state function is determined by Schrödinger’s Equation
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“Weirdness” of QM Things are quantized
– The radius of the Earth’s orbit can’t be changed by an arbitrarily small amount
Waves don’t have to be in one place– Interferometry
More generally – superposition– Schrödinger’s cat
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Thought QuestionI put a cat into an ideal box (one which no
information can flow in or out of) with a bottle of poison. A device in the box will open the bottle and kill the cat when a radioactive atom decays. After the cat has been in the box for a time t, is the cat dead or alive?
A – Yes B – No
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Why do I care? Need it to understand
– Small things (like transistors in computer chips and red blood cells, for example)
– “Degenerate” things (like laser beams and neutron stars)
You can do some interesting things with QM– Quantum computation– Quantum encryption / key distribution
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Notation Atomic number-Z, # of protons in the nucleus
Determines which element it is Neutron number-N, # of neutrons in nucleus Mass number- A=Z+N
AZX
Isotopes—Nuclei of the same element (same Z) with different A (and N) values.
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How many Protons does 263
106Sg have?
A. 263B. 106C. 157D. 42E. I can’t tell because I do not know where Sg
is on the periodic table.
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How many Neutrons does 263
106Sg have?
A. 263B. 106C. 157D. 42E. I can’t tell because I do not know where Sg
is on the periodic table.
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How many electrons does 263
106Sg have?
A. 263B. 106C. 157D. 42E. I can’t tell because I do not know where Sg
is on the periodic table.
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Nuclear Strong Forcea short range attractive force
between nuclear particles Holds the atom together Very short range—almost touching If the distance between two protons
is >10-15 m then the coulomb repulsive force is too strong and the nuclei breaks apart.
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THE TEN VIRGINSThey WERE prepared for the coming of the bridegroom. What they weren't prepared for was . . .
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Radioactive Half Life
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Discussion Question: You start with 1000 dice. Every time you get a six you take it out. How many rolls is a half-life?A. 2B. 4C. 6D. 8E. 10
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If I start with 10000 pennies and every time I toss all the coins I remove the tails, how many tosses does it take to
get down to less than a dollar left?A. 3B. 5C. 7D. 9E. 11
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For radioactive decay where No
is the number of nuclei you start with and N is the number of nuclei after a time t
toeNN
How do I solve for λ?