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Physics Sg Lab Report

Autor:   •  May 25, 2019  •  Study Guide  •  728 Words (3 Pages)  •  17 Views

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  • Doppler effect: observer behind source hears lower pitch (longer wavelength)[pic 1]

                     observer in front of source hears higher pitch (shorter wavelength)

  • sound waves are more commonly shifted than light waves
  • p waves- fastest of 3 (longitudinal, pressure, can go through liquid)
  • s waves- 1/2 as fast as ^ (transverse, secondary, can’t go through liquid)
  • L waves- slowest of 3 (combo, L= s + p) its amplitude determines the Richter magnitude of an earthquake
  • L = travel on surface // S and P travel on surface OR underground
  • categorized in different ways:
  1. how they travel
  • matter or mechanical waves- must move through substances/ material (like earthquakes)
  • energy or electromagnetic waves- can pass through a vacuum (light, heat)
  1. how they’re generated
  • longitudinal- parallel// matter waves// sound + shock waves// can propagate in solids, liquids, & gases
  • transverse- perpendicular// energy waves// all forms of electromagnetic radiation (gamma, UV, when a crowd does the wave)// can propagate only in solids
  • transmission medium- what wave passes through (earthquake=ground; music= air) determines speed of wave
  • interference does not destroy the component waves. they mix, un-mix, and continue (ex. headlights)
  • incident wave enters at the same angle that reflected wave bounces off
  • high impedance = out of phase = most energy bounces back

Ch 14

  • all sounds are caused by a vibration of some kind and speed of sound is generally greatest in solids
  • sound waves in gases and liquids are primarily longitudinal
  • sound waves in solids can have both transverse and longitudinal components bc intermolecular interaction in solids are much stronger// solids > liquids > gases in elasticity
  • nodes- points of completely destructive interference
  • antinodes- points of completely constructive interference
  • standing waves- other waves transmit energy not matter// this doesn't transmit energy or momentum
  • pure standing waves are formed by only 2 things: tuning fork and electronic keyboard// has a pattern
  • noise is different from standing wave bc there is no pattern
  • sympathetic vibration- an oscillation induced in an object by indirectly driving at its fundamental frequency
  • conditions for resonance: the wavelength must have a whole number of wave segments fit on the string
  • segments- the portion of the string between adjacent nodes
  • when string is plucked in middle it vibrates at natural frequency (lowest freq that can sustain a standing wave)
  • fundamental frequency = resonant = natural = 1st Harmonic// things can have more than 1 natural frequency
  • amplitude = loudness// frequency = pitch/ note
  • audible region = 20 - 20k Hz// there is a limit in the sound spectrum (one gigahertz)
  • frequencies lower than 20 = infrasonic range (ie. nature, earthquakes)
  • higher than 20k = ultrasonic// can travel for km in water so used in sonar// (ie. crystals, seafloor imaging)
  • audibility threshold- quietest sound you can hear// pain threshold- loudest sound not producing pain
  • intensity- the amount of energy entering an area in a certain amount of time
  • intensity level- comparison of a sound’s loudness to a standard (that standard = audibility threshold)
  • both the loudness AND duration of a sound affect hearing loss
  • sonic boom- when something’ s traveling at speed of sound, a large # of waves overlap & produce many points of constructive interference which form a shock wave & when the shock wave passes over someone, the large concentration of energy produces a sonic boom// doesn't only occur when plane breaks sound barrier
  • Mach- number greater than one indicates supersonic speed and less than one indicates subsonic. Number 2 indicates a speed twice the speed of sound


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