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Wave Phenomena

Wave Phenomena

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Wave Phenomena

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  1. Wave Phenomena Wu, Jinyuan Fermilab Aug. 2013

  2. Introduction • We will talk about classical physics only. • We will try to show phenomena not commonly seen in text book. Many pictures in this file are taken via www.google.com They are used for review and comments only. Wave Phenomena

  3. Oscillation of Things Wave Phenomena

  4. Repetitive Motions of many Things • We live in a world with two type of motions: • One pass motions. • Repetitive motions. Wave Phenomena

  5. Inertia and Recovery Force of Oscillations • An object needs two elements in order to oscillate: • Recovery force: so that the object moves back and forth around an origin. • Inertia: so that the object keeps moving. Wave Phenomena

  6. Boundary Conditions and Eigen Values “DO” “SO” • When an object is supported differently, the resonant frequencies can different. • Different boundary conditions causes different movement modes with different Eigen Values Wave Phenomena

  7. Frequency vs. Length • F = const. x (1/L) • Guitar • Violin • Organ • F = const. x (1/L)2 • Xylophone • F ~ const. x (1/L)0 • Rubber band string Wave Phenomena

  8. Multi-wire Chambers (1) • When a charged particle passes through, the gas in the multi-wire chamber is ionized. • Electrons drift toward signal wires under electrical field generated by the high voltage wires. • When the electrons arrive the signal wires, electrical pulses are detected. • From arrival time, the track position can be determined. Wave Phenomena

  9. Multi-wire Chambers (2) • Several planes of multi-wire chambers can be used to determine the track direction. Wave Phenomena

  10. Straw Tube Chambers • The wire can be stretched in a plastic tube with metalized walls. Wave Phenomena

  11. Wire Tension Measurement • Wires must be stretched to certain tension to hold their positions. • To measure the wire tension, a pulse of current is sent through the wire in a magnetic field. • The resonant frequency is recorded to calculate the wire tension. Wave Phenomena

  12. Reflection of Waves Wave Phenomena

  13. Reflection • Waves reflect at the boundary of two media. Wave Phenomena

  14. Retro-reflection (1) Animal Eyes Wave Phenomena

  15. Retro-reflection (2) Mirror Corner • Show the retro-reflectivity of the mirror corner. (using <10 lines) Wave Phenomena

  16. Retro-reflection (3) Glass Ball a b Wave Phenomena

  17. Glass Balls with Different n • When the index of refraction is ~2, most incident light will reflect back. Wave Phenomena

  18. Glass Ball Submerged in Water • When the glass ball is submerged in water, relative index of refraction becomes ~ 2/1.33 = 1.5 • Most incident light will reflect away. • The highway lane paint is difficult to see in rainy nights. Wave Phenomena

  19. Impedance of Co-axial Cables Wave Phenomena

  20. Impedance Mismatch & Optical Reflection • The reflection seen above is due to difference of the impedances (not index of refraction!) of media. Wave Phenomena

  21. Acoustic Impedance Mismatch for Muffler Impedance Mismatch Impedance Mismatch Impedance Mismatch Impedance Mismatch Wave Phenomena

  22. Sound Wave Reflection at the Tube End • Large fractions of sound waves reflect back and forth in a tube. • Different tube lengths cause different resonant frequencies. • Small amount of sound waves come out from the tube end or the bell of the brass instrument. • Sound waves reflect at not only closed, but also open ends of tubes. Wave Phenomena

  23. Signal Reflection in an Open Cable • Cables are usually terminated at the end to eliminate signal reflection. • An open cable causes a reflected waveform with same polarity as the transition signal. Wave Phenomena

  24. An Application: CAKE Clocking w 1 2 1 dA 3 2 3 R 1+3 w V/4 dA w+2dA w 2 1 1 dB TDC 3 2 3 R 1+3 dB V/4 w+2dB • When a signal is sent through a cable, the cable lengths can be different and may change with temperature. • When the pulse is allowed to reflect back, a cake shaped signal is seen at the transmitting end. • The width of the cake base can be used to monitor cable lengths. TDC Wave Phenomena

  25. Oscilloscope View of the CAKE • Two cables with different lengths are used. • CH1 & 3: Transmitting ends. • CH2 & 4: Receiving ends. • Cake shaped pulses are seen at the transmitting ends. Wave Phenomena

  26. Why a medium has two independent wave properties? • A medium has two independent wave properties: • Speed of wave, or index of refraction • Impedance • An oscillation is a process of energy exchange between two energy formats: • Kinetic energy and potential energy • Electrical energy and magnetic energy • The responses of a media to the two energy formats produce two independent wave properties. Wave Phenomena

  27. Cherenkov Radiation Wave Phenomena

  28. Shock Wave of Supersonic Objects • When an object is faster than the speed of sound in air, a shock wave is generated. • Bursting balloon: sonic boom. • Sneezing: 31 m/s. Initial speed could be higher. Wave Phenomena

  29. Visible Shock Waves • Supersonic objects cause shock waves. • Shock waves cause the water vapor to condense into small ice crystals. Wave Phenomena

  30. Wake Waves of High Speed Boats • When the speed of a boat is faster than the speed of water wave, a strong wake wave is generated. Wave Phenomena

  31. Cherenkov Radiation Generated by Fast Charge Particle • When a charged particle moves faster than speed of light in a medium, Cherenkov light is generated. • Faster than speed of light? It is OK in a medium: • Speed of light in water: (1/n)*c = (1/1.33)*c = 0.75 c. • Electron at 10 MeV: 0.998 c. • Proton at 5 GeV: 0.98 c. Wave Phenomena

  32. Cherenkov Counter Using Gas PMT Array pion proton • When a particle with speed higher than (1/n)*c passes through the gas, Cherenkov light is generated. • Curved mirror focus the light to the photo-multiplier tube (PMT) array. • Particle species can be identified. • The index of refraction n is adjusted by changing the pressure of gas. Wave Phenomena

  33. Observation of Cherenkov Light in Atmosphere • Cherenkov light can be generated in atmosphere when cosmic ray particles pass through. Wave Phenomena

  34. Cherenkov Light in Liquid • Super-Kamiokande water Cherenkov detector Wave Phenomena

  35. Cherenkov Light in Solid SiPM • The detector is used to detect high energy protons for LHC experiments at CERN. • Cherenkov light is generated in fused quartz. • Generated light is under total reflection inside the L-shaped bar. (Therefore the index of fraction of the medium must be > 1.414. ) • The light reach the silicon photo multiplier (SiPM) and a electrical pulse is generated. Wave Phenomena

  36. Multiple Waves in Media Wave Phenomena

  37. Waves in Media • Two lights (ordinary and extraordinary) in a crystal have different speed and polarizations. • Two acoustic waves can be generated in an isotropic solid. • Three acoustic waves can be generated in a crystal. Wave Phenomena

  38. Lights in a Calcite Crystal • Lights with different polarizations have different speed in a Calcite crystal. • The phenomenon is called birefringence (double refraction). Wave Phenomena

  39. Earthquake • The P wave generated by an earthquake arrives earlier than S wave in a seismogram. • The distance of the earthquake focus can be estimated from the arrival time difference of the P and S waves. Wave Phenomena

  40. Color on Plastic CD Box sky It is not due to interference on thin film. Wave Phenomena

  41. Birefringence (Double Refraction) Due to Internal Stress (Photoelasticity) Wave Phenomena

  42. The Residual Stress in CD Box Wave Phenomena

  43. The Residual Stress in Plastic Film Wave Phenomena

  44. The Sky as a Polarizer Wave Phenomena

  45. Polarization of Reflection Brewster Angle Wave Phenomena

  46. Colors Due to Multiple Effects sky • Polarized lights are generated in the sky due to scattering. • Residual stress in plastic causes double refraction. • Double refraction causes polarization plane to rotate and the amount of rotation is a function of the wavelength. • Reflectivity of the plastic surface depends on the direction of the polarization. Wave Phenomena

  47. Complexity (or Fun) of Wave Physics Wave Phenomena

  48. Complexity of Wave Physics Tsunami College Optics Earthquake • Solid media cause more waves interacting each other. • Speeds of waves may depend on the wavelength, i.e., dispersive. • Large amplitudes cause the wave equations become non-linear or even chaotic. Wave Phenomena

  49. Nonlinear Optics • There are many amazing effects in nonlinear domain. • Frequency of waves can be doubled in nonlinear crystals. • When a 1064 nm (infrared) laser is sent through a nonlinear optical crystal (KDP), a 532 nm light (green) can be generated. Wave Phenomena

  50. Geological Strata • The earthquake waves travel in layered solid media. • The media are usually simplified as isotropic. Wave Phenomena