CHEM 110 Lecture Notes - Lecture 2: Photon, Ernest Rutherford, Plum Pudding Model
September 8, 2017
Quantum Mechanics - Light
CHEM 110
-History of Light:
•No substructure: measurements did not agree with classical theory
•Experiments didn't disagree
-Light:
•All stuff emits light
•Light & matter are related
•Amplitude = intensity
•Wavelength = distance between similar parts of a wave
•Velocity = c = 3x108 m/s
•Radiation exists across 14 orders of magnitude ( we can’t see all of them)
-Gamma rays, X-rays, UV, infrared, microwave, radio frequency
-Blackbodies:
•Everything emits light!
•No reflection, emits a perfect color black
•Like a black hole
•Check out PHET: interactive online simulations
•Everything with a temperature gives off the same curve
•You are glowing! —> need a special device to see wavelengths in micrometers
•Peak of wavelength is around 10 microns (T = 310K)
•Such devices are used in the military
-Blackbody Radiation:
•The sun’s emission is a perfect blackbody
•You need to match environment’s temperature to been unseen in special cameras
•0K does not emit light
•Rayleigh-Jeans law was wrong —> experimental data shows the curve is correct
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Document Summary
History of light: no substructure: measurements did not agree with classical theory, experiments didn"t disagree. Gamma rays, x-rays, uv, infrared, microwave, radio frequency. Blackbodies: everything emits light, no re ection, emits a perfect color black, like a black hole, check out phet: interactive online simulations, everything with a temperature gives off the same curve, you are glowing! > need a special device to see wavelengths in micrometers: peak of wavelength is around 10 microns (t = 310k, such devices are used in the military. Photoelectric effect: albert einstein (nobel prize for this, shine light on metal > get electric current. When you increase energy of the light, it goes into k energy of the electron: einstein invented the photon, planck"s constant = 6. 6 x 10-34 js. Bunsen-kirchhoff experiment: hot matter gives off light, cold matter absorbs wavelengths, metals glow at an exact frequency, black bands = no light has arrived, absorbed by atmosphere. J. j. thompson: discovered the electron 1897.
