Transcript Document
Chapter 40 Serway & Jewett 6th Ed. Approximate Total Absorption Cavity Stefan- Boltzman Law I = T4 = 5.6699 10-8 W/m2-K4 Ultraviolet Catastrophe I 2ck BT 4 Classical expression Quantized Energy Levels of a Harmonic Oscillator Photoelectric Effect Fig 40-9, p.1292 Photoelectric Effect Table 40-1, p.1294 Electrons interacting with light Classical Picture F qv B qvBkˆ Just dipole radiation independent of ! Electrons interacting with light Quantum Picture 'o h 1 cos me c Compton Scattering Atomic Spectra Hydrogen Nitrogen Balmer’s Realization DeBroglie Wavelengths The Davisson-Germer experiment showed that electrons exhibit the DeBroglie wavelength given by: k1 – k2 = k k1 + k2 = k 1 – 2 = 1 + 2 = Wavepacket A cosw t i i i Delayed Choice Depending on how we do the experiment we determine what happens! Superposition States c1 1 c2 0 = + = Measurement One and only one of or Photons are emitted on opposite sides of the pump beam, along two cones. One of cone has horizontal polarization and the other of has vertical polarization. Photon pairs emitted along the intersections of the cones are entangled in polarization -- each photon is individually unpolarized, and yet the photons necessarily have perpendicular polarizations, no matter how far apart they are! http://www.physics.uiuc.edu/People/Faculty/profiles/Kwiat/index.html Quantum Weirdness! What is Schrodinger's Cat Paradox? Schrodinger's Cat (in his own words) "One can even set up quite ridiculous cases. A cat is penned up in a steel chamber, along with the following diabolical device (which must be secured against direct interference by the cat): in a Geiger counter there is a tiny bit of radioactive substance, so small that perhaps in the course of one hour one of the atoms decays, but also, with equal probability, perhaps none; if it happens, the counter tube discharges and through a relay releases a hammer which shatters a small flask of hydrocyanic acid. If one has left this entire system to itself for an hour, one would say that the cat still lives if meanwhile no atom has decayed. The first atomic decay would have poisoned it. The Psi function for the entire system would express this by having in it the living and the dead cat (pardon the expression) mixed or smeared out in equal parts. It is typical of these cases that an indeterminacy originally restricted to the atomic domain becomes transformed into macroscopic indeterminacy, which can then be resolved by direct observation. That prevents us from so naively accepting as valid a "blurred model" for representing reality. In itself it would not embody anything unclear or contradictory. There is a difference between a shaky or out-of-focus photograph and a snapshot of clouds and fog banks." -- Erwin Schrodinger Translation by John D. Trimmer Basically what Schrodinger is saying is that because of the way the experiment is set up, the cat has a 50% chance of being alive, and a 50% chance of being dead. It is just as likely that the cat is alive as that it is dead, so Schrodinger said that until the box is opened, the cat is both alive and dead. This is obviously false, the cat cannot be both alive and dead at the same time. This problem is meant to illustrate a theory of quantum mechanics called "indeterminacy." Indeterminacy says that there can be more than one correct answer to a problem which physically can only have one answer. Schrodinger came up with this illustration to demonstrate that there was a problem with this theory of quantum mechanics.