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Waves. Part II: Behavior. Standing Waves. Standing waves are a result of interference. Combination of incident and reflected waves Two waves of equal amplitude and wavelength pass in opposite directions. Node – stationary point where waves are always out of phase.
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Waves Part II: Behavior
Standing Waves • Standing waves are a result of interference. • Combination of incident and reflected waves • Two waves of equal amplitude and wavelength pass in opposite directions. • Node – stationary point where waves are always out of phase. • Antinode – largest point of amplitude The Wave Machine http://www.cbu.edu/~jvarrian/applets/waves2/simwav_g.htm
Standing Waves Due to interference Nodes “out of Phase” Antinodes “In phase”
Interference - waves combine Destructive or Constructive Interference http://users.erols.com/renau/wave_interference.html
Principle of Superposition • When two or more waves meet, there is interference. • The displacement caused by two or more waves is the algebraic sum of the individual waves • Constructive interference – waves in phase add • Destructive interference – waves out of phase subtract
Reflection • When wave reaches a barrier at least part of the wave bounces back. • Angle of incidence equals the angle of reflection • http://www.physicsclassroom.com/mmedia/waves/fix.html
Change in Media • A place where the substance the wave is traveling through changes • Example: A light wave traveling through air passes through a glass window • Some of wave is transmitted and some is reflected
Refraction • When a wave travels in a different medium the velocity changes • This change in velocity results in bending of the wave. • This is why a pencil appears to bend in a glass of water.
Diffraction • Waves normally travel in a straight line in a medium. • When waves meet a barrier, they bend around the edges. • This is called diffraction. • http://www.control.co.kr/java1/masong/oneslit.html
The Doppler Effect • The apparent change in frequency of a wave due to the motion of the source or receiver. • Greater speeds produce greater effects. http://library.thinkquest.org/19537/java/Doppler.html http://www.control.co.kr/java1/masong/doppler.html
Doppler effect - Examples • car horn • sirens • radar gun • light • increase frequency – blue shift • decrease frequency – red shift