Waves
Dec 20, 2015
Waves
What Is a Wave?A disturbanceTransmits energy not matterThrough matter and space
Medium-matter through which a wave travelsSound waves require a medium
Waves Transfer EnergyWaves can do work
ExamplesSand Eardrum
• Eye, photo film
Sound When sound travels in the air, the waves spread out as spheresAs they travel outward they get bigger
Longitudinal Wave
Vibrations of the drum head create sound waves in the air
Sound Waves Are Pressure Waves
Pressure nodes appear symmetrically at each endOpen to the atmosphere
Standing Wave
Fundamental frequency for each pipeWavelength = = 2LFrequency = f = v / 2LShorter the length higher the frequency
Harmonics
= L
f = v / L
Even numbered multiples of the fundamental
Pitch
Large wavelength ->Low frequency ->Low pitchSmall wavelength ->High frequency ->High pitch
Moving Sound SourceAs the source of a wave movesThe wave fonts bunch up in frontSpread out behind
The Doppler Effect
What if the disturbance is traveling at the same speed as the wave fronts?
What if the disturbance is traveling faster than speed of the wave fronts?
Bow Wave
Bow Waves
Period
Time required for a full wavelength to passSymbol is TSI unit is seconds
FrequencyFrequency measures the rate of vibrations
periodfrequency
1
Tf
1
Frequency
Number of vibrations that occur in an 1 sec time interval
Period – the time required for one full wavelength to pass a certain point