Parts of wavesParts of waves

2 Parts Transverse Wave2 Parts Transverse Wave

1) Crest – high point of wave1) Crest – high point of wave 2) Trough – low point of wave2) Trough – low point of wave

2 Parts of Compressional Wave2 Parts of Compressional Wave

1) Compression – medium is crowded together & 1) Compression – medium is crowded together & more densemore dense

2) Rarefaction – less dense region2) Rarefaction – less dense region

Wavelength – Wavelength – distance between 1 point on distance between 1 point on a wave and the nearest point just like it on the a wave and the nearest point just like it on the

next wavenext wave

Transverse – 1 crest to next crest OR 1 trough to Transverse – 1 crest to next crest OR 1 trough to next troughnext trough

WavelengthWavelength

Compressional – 1 compression to next OR 1 Compressional – 1 compression to next OR 1 rarefaction to nextrarefaction to next

Ex. Wavelength of sound waves range from few Ex. Wavelength of sound waves range from few cm for high pitch to about 15m for deep soundscm for high pitch to about 15m for deep sounds

Frequency - # of wavelengths that pass a Frequency - # of wavelengths that pass a fixed point each secondfixed point each second

Units – hertz (Hz) 1Hz = 1/sUnits – hertz (Hz) 1Hz = 1/s As frequency increases wavelength As frequency increases wavelength

decreasesdecreases Period – amt of time it takes 1 wavelength to Period – amt of time it takes 1 wavelength to

pass a point pass a point Units – seconds Units – seconds As frequency increases the period As frequency increases the period

decreases decreases

Wave speedWave speed

Also called velocity of propagationAlso called velocity of propagation Light waves travel faster than sound ex. Light waves travel faster than sound ex.

You see lightning before you hear thunderYou see lightning before you hear thunder Depends on mediumDepends on medium When temp. of medium increases sound will When temp. of medium increases sound will

travel fastertravel faster

Sound waves – usually travel faster Sound waves – usually travel faster in liquids & solids than in gasesin liquids & solids than in gases

Light waves – travel more slowly in liquids & Light waves – travel more slowly in liquids & solids than in gases or in empty spacesolids than in gases or in empty space

Speed = (frequency)(wavelength)Speed = (frequency)(wavelength) V = fV = f Sample Problem: What is the speed of a Sample Problem: What is the speed of a

sound wave that has a wavelength of 2.00m sound wave that has a wavelength of 2.00m & a frequency of 170.5Hz?& a frequency of 170.5Hz?

1) A wave traveling in water has a frequency 1) A wave traveling in water has a frequency of 500.0Hz & a wavelength of 3.0m. What is of 500.0Hz & a wavelength of 3.0m. What is the speed of the wave?the speed of the wave?

2) The lowest pitched sounds humans can 2) The lowest pitched sounds humans can hear have a frequency of 20.0Hz. What is hear have a frequency of 20.0Hz. What is the wavelength of these sound waves if their the wavelength of these sound waves if their wave speed is 340.0m/s?wave speed is 340.0m/s?

3) The highest pitched sounds humans hear 3) The highest pitched sounds humans hear have a wavelength of 0.017m in air. What is have a wavelength of 0.017m in air. What is the frequency of these sound waves if their the frequency of these sound waves if their wave speed is 340.0m/s?wave speed is 340.0m/s?

AnswersAnswers

1) v = frequency x wavelength1) v = frequency x wavelength (500Hz)(3m)(500Hz)(3m) 1,500m/s1,500m/s2) Wavelength = speed / frequency2) Wavelength = speed / frequency 340m/s / 20Hz340m/s / 20Hz

17m17m3) Frequency = speed / wavelength3) Frequency = speed / wavelength 340m/s / 0.017m 340m/s / 0.017m 20,000Hz20,000Hz