Chapter 25 Intro to Waves 12 17 2009 Waves are transfer of energy Waves Disturbance The material being disturbed is the MEDIUM o The medium only vibrates it does NOT move along with the wave o Is any solid liquid or gas o Moving water o Highest point of the wave Current Crest Trough Cycle Period o Lowest point on the wave Amplitude o Height of the wave o 1 crest followed by 1 trough o How fast 1 cycle is Wave length o Distance of 1 cycle Frequency o Number of cycles per second CPS Hertz o 1 cycle 1 second 1 hertz Hz Two types of waves o Medium vibrates at right angles to direction of wave Transverse Water light Longitudinal compression o Medium vibrates parallel to direction of waves Sound Shock wave When an object moves through medium faster than the wave makes it o Wake of a boat is a shock wave A shock wave by an object moving faster than sound o Crack of a whip is a sonic boom Sonic boom Sound Waves Type o Compression Medium Speed o Gas solids liquid o Air 600 700 mph o 1100 ft sec o about 5 sec mi o faster in liquids and solids Frequency o 20 CPS 20 000 CPS Above 20 000 CPS Ultra sonic o 1 Sonar o 2 Bug deterrent o 3 Clean jewelry o 4 Medicine o 5 Burglar alarm Resonant Frequency Natural frequency of vibration of an object o Greater the mass lower the frequency 2 ways to get an object to vibrate o 1 Tap it o 2 Place a source of sound nearby that is resonating at natural frequency of vibration of the object o 12 17 2009 12 17 2009
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