lecture9

lecture9 - Physics 126 Lecture 9 March 7 and 9 2011 What is...

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.Loy, H. B. Chan 1 Physics 126 Lecture 9 March 7 and 9, 2011 What is X-Ray? X-ray Diffraction: X-ray is WAVE! Compton Scattering: X-ray is PARTICLE! Suggested Reading: Ch. 2.5-2.8 p Review of Wave and EM Wave, Polarizations of Wave p X Ray Diffraction. Wave nature and periodic structure of crystals. X-ray spectrometer p Compton Scattering: X-Ray is Particle p Pair Production and Pair Annihilation p X-Ray Wave? X-Ray Particle?
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.Loy, H. B. Chan 2 Two Broad Themes: What is Matter? What is Radiation (light)? What is Matter? Electrons, X-Ray, Radioactivity, atomic nature of matter, atomic nucleus ( Quantization of Matter) (Lec 7) What is radiation (including light, infra red heat wave, etc)? Statistical Mechanics and Radiation (light): Energy is ‘quantized’ Quantization of Light . (Lec 8) X-Ray diffraction and X-Ray spectra . Radiation (light) is wave ! Compton scattering Radiation is particle! Einstein’s quantum theory of radiation. Radiation is particle with energy and momentum! Particle – Wave duality for light Matter is wave . Particle – Wave duality for matter (Lec 10) The New Quantum Mechanics
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.Loy, H. B. Chan 3 What exactly is X-Ray? Particle? Wave? Useful only for seeing broken bones and bullet wounds? World wide craze already in 1896! 1896 X ray picture of tropical fish
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.Loy, H. B. Chan 4 X- Ray Tubes: High Energy Electrons hitting a target “Anticathode” The Original (1895) ~1915 Need electrons high voltage to accelerate the electrons Target material makes a difference What is X-Ray? Wave or Particle?
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.Loy, H. B. Chan 5 What is a Wave? b Webster's dictionary defines a wave as "a disturbance or variation that transfers energy progressively from point to point in a medium and that may take the form of an elastic deformation or of a variation of pressure …” Only the disturbance or variation (that transfers energy) moves. There is no net transfer of mass !
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.Loy, H. B. Chan 6 A wave is not localized b Single oscillator can emit wave to fill all space. The energy is spread out to all space. (1/r 2 ) b Note that the points in the picture only move back and forth: none of them move off the page even though the waves keep moving outward. b A wave is characterized by: 1. frequency 2. wavelength 3. amplitude of oscillation b Properties of wave: diffraction, interference, reflection
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.Loy, H. B. Chan 7 Superposition Principle for Waves: Two or more waves can superpose to form another wave. Constructive or destructive interference Standing Wave Beat Wave
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.Loy, H. B. Chan 8 What is a Particle? A mass of matter that can be treated as a point. A particle is localized in space, has mass, momentum and energy. A particle: where it is, how fast it is going, and what direction it is going, etc.
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.Loy, H. B. Chan 9 Unlike waves, particles have no interference effect, no superposition principle. VERY DIFFERENT! b
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This note was uploaded on 03/31/2011 for the course PHY 126 taught by Professor Hobunchan during the Spring '11 term at HKUST.

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lecture9 - Physics 126 Lecture 9 March 7 and 9 2011 What is...

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