#  A vibration that repeats regularly in space and time  Transmitted from one place to another w/out actually transporting matter  A transmission of.

## Presentation on theme: " A vibration that repeats regularly in space and time  Transmitted from one place to another w/out actually transporting matter  A transmission of."— Presentation transcript:

 A vibration that repeats regularly in space and time  Transmitted from one place to another w/out actually transporting matter  A transmission of Energy  Require a medium (substance to travel through)  Ex. Water waves, sound, wave in string/spring

 Wavelength – (λ) – distance between identical parts of a wave. Length of wave  Amplitude (A)– height of a wave  Period (T) - time for one full wave to pass  Frequency (f) – cycles per second … how many full waves pass by per second

 Frequency = 1/ Period  Period = 1 / Frequency  Reciprocals of each other….  Waves per time (frequency)  Time per wave (Period)

 Any regularly repeating vibration  Pendulum  Spring  Vibrations caused in buildings by wind  Steps of a person walking  Rules for waves can be used for anything that fits in this category

 Transfers energy not matter  If stone dropped in water, the disturbance moves not the water

 Wave speed depends on the medium  The more rigid the medium the faster sound will travel through it  Wave speed = frequency X wavelength  v = f λ

 Medium vibrates in a directions perpendicular to the direction of the wave

 Medium vibrates in the same direction that the wave moves

 Constructive Interference  Waves can interfere w/ each other so that they add together to produce a larger wave  Destructive Interference  Waves can interfere w/ each other so that they subtract each other and cancel out  Demos

Out of phase – Destructive interference In phase – Constructive interference

 When waves collide w/ a barrier they have a tendency to wrap around the barrier  Break walls at the beach  This is why we can hear a person talking even if they are around the corner

 Tsunamis are large waves generated by a large earthquake or massive landslide  Travel at hundreds of miles per hour, have low amplitudes out at sea, but can become very high when approaching shore

 Longitudinal wave  Sound travels as a region of compressed air  The areas in between compressed regions are called “rarefactions”  Speed of sound is about 340 m/s in air  Like any wave the speed depends on the medium

 Frequency of a sound wave affects the “pitch” or how we hear a sound  Higher frequency, higher the pitch  Humans can typically hear pitches ranging from 20 Hz (infrasonic) to 20,000 Hz (ultrasonic), but that range diminishes as you age… typically at the high end  Loudness of a sound is affected only by amplitude

 http://www.cbu.edu/~jvarrian/applets/dopp ler1/doppler.htm http://www.cbu.edu/~jvarrian/applets/dopp ler1/doppler.htm  http://www.youtube.com/watch?v=AXhRmv1 mrs4&safe=active http://www.youtube.com/watch?v=AXhRmv1 mrs4&safe=active  Hearing test  http://en.wikipedia.org/wiki/52- Hertz_whale http://en.wikipedia.org/wiki/52- Hertz_whale  lonely whale  http://www.youtube.com/watch?v=h5l4Rt4O l7M&safe=active http://www.youtube.com/watch?v=h5l4Rt4O l7M&safe=active  Hearing test

 Waves From an object that is approaching have short wavelength, which means they have a higher freq. And a higher pitch  waves coming from an object that is moving away from you have a longer wavelength and therefore a lower freq, and lower pitch  Cars approaching and leaving

 Sometimes the source of a wave can travel faster than the waves it is creating  http://www.youtube.com/watch?v=6o0zmaf xTmE&safe=active http://www.youtube.com/watch?v=6o0zmaf xTmE&safe=active  Can be easily seen with a speed boat  http://www.youtube.com/watch?v=2Sv4o4Kk tm4&safe=active http://www.youtube.com/watch?v=2Sv4o4Kk tm4&safe=active  Sonic boom created when a object or plane breaks through the sound barrier

Standing waves Stationary wave caused by interference between a wave and its reflection – Two waves of equal amplitude and wavelength pass through each other in opposite directions. Nodes – stationary points – Where waves our “out of phase” --- crest lined up with trough Antinodes- points of largest amplitude – Where waves are “in phase” - crest lined up with crest Standing Wave in Water Standing wave demo Standing waves created by speaker Swimming pool When an object is forced into vibrating at one of its natural frequencies, it vibrates in a manner such that a standing wave is formed within the object.