Download Introduction to Quantum Mechanics - Calculus Based Physics I | PHYS 2110 and more Study notes Physics in PDF only on Docsity! Ch 40 Introduction to Quantum Mechanics 40.1 Blackbody Radiation & Planck's Hypothesis A blackbody is an object that absorbs all radiation incident upon it, but you can think of it as an object at uniform temperature. Both the peak wavelength emitted & the amount of radiation emitted at a given wavelength depend upon the temperature. We can model the relationship between temperature and the peak intensity's wavelength with "Wein's Law:" Title: Apr 27 8:03 AM (1 of 7) Classical Picture: (try to explain with Newton & Maxwell) Thermal motion of charged (electrons/ions) near the surface emit electromagnetic (EM) radiation like small antennas resonating. However, this predicts an increasing amount of radiation at shorter λ's that isn't seen in experimentsthe "ultraviolet catastrophe" Enter Max Planck (1900), who proposed the following: each of these "resonators" can only have discrete energies the energy comes out in discrete "packets" named photons (by Einstein, 1905) when a resonator changes energy levels. Title: Apr 27 8:29 AM (2 of 7) momentum & energy of the incoming photon: for the outgoing photon: The electron also picks up some kinetic energy & momentum. Apply conservation of momentum & kinetic energy The classical picture and the quantum picture make different, specific predictions about the scattered xrays. Observations are consistent with the quantum picture & not the classical picture> more evidence that energy is energy is quantized & comes in "packets." Title: Apr 27 9:24 AM (5 of 7)
40.4 Photons & EM Waves
Principle of complementarity:
Light (and EM radiation, energy in general) exhibits the
properties of both a wave & a particle (but not at the same
time).
Light is both a wave & a particle, not either/or.
Title: Apr 27 - 9:38 AM (6 of 7)
HW (due Wed 4/29--last homework due)
Ch 40 pp 1314-1316:
P 2, 7ab, 9, 31
Title: Apr 27 - 9:54 AM (7 of 7)
