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