L03 - Dr. P. Lucas U of A MSE 110 Quantization SUMMARY FROM...

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Unformatted text preview: Dr. P. Lucas U of A MSE 110 Quantization SUMMARY FROM LAST CLASS • Duality wave/particle of light: light can and should be described as both a particle and a wave. • Wave : Oscillating E field with wavelength, frequency, amplitude velocity, phase (all characteristics of a wave). • Particle : Photons have no mass but carry an energy E=h υ and have momentum p=h/ λ . (all characteristics of a particle). • Photoelectric effect demonstrates that energy is quantized: energy can only be transferred in packets (quanta). • : photon energy (h υ ) transferred to the electron to extract it ( Φ ) and provide kinetic energy (½mv 2 ). • : at the stopping voltage V s , no electron have enough kinetic energy to reach the cathode, the current=0. • De Broglie’s principle: any moving object with mass m and velocity v can also be described as a wave with a wavelength equal to: • This principle is necessary because classical physics failed to explain 2 2 1 v m h e + Φ = υ s e V e v m ∆ = 2 2 1 mv h = λ the behavior of small particles. (needed only if λ ≈ size of object). Dr. P. Lucas U of A MSE 110 Atomic spectra: Balmer series QUANTIZED ATOM • 1885: Balmer used gas discharged tubes to study the light emitted by gas of atoms (hydrogen, neon, argon, mercury) • Gas introduced in a vacuum tube with metal electrodes. • High-voltage is applied, gas atoms absorb energy and get “excited”. • This results in light emission, the gas glows. Ne Ar Hg • Different gas emit different light. • This is the principle of neon signs • This is called a gas discharge tube . Dr. P. Lucas U of A MSE 110 Atomic spectra: Balmer series QUANTIZED ATOM • Balmer studied the light emitted by several monoatomic gas, the atomic spectra of gases....
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This note was uploaded on 11/19/2009 for the course MSE 110 taught by Professor Lucas during the Spring '08 term at University of Arizona- Tucson.

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L03 - Dr. P. Lucas U of A MSE 110 Quantization SUMMARY FROM...

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