Parts of waves

2 Parts Transverse Wave  1) Crest – high point of wave  2) Trough – low point of wave

2 Parts of Compressional Wave  1) Compression – medium is crowded together & more dense  2) Rarefaction – less dense region

Wavelength – distance between 1 point on a wave and the nearest point just like it on the next wave  Transverse – 1 crest to next crest OR 1 trough to next trough

Wavelength  Compressional – 1 compression to next OR 1 rarefaction to next  Ex. Wavelength of sound waves range from few cm for high pitch to about 15m for deep sounds

 Frequency - # of wavelengths that pass a fixed point each second  Units – hertz (Hz) 1Hz = 1/s  As frequency increases wavelength decreases  Period – amt of time it takes 1 wavelength to pass a point  Units – seconds  As frequency increases the period decreases

Wave speed  Also called velocity of propagation  Light waves travel faster than sound ex. You see lightning before you hear thunder  Depends on medium  When temp. of medium increases sound will travel faster

Sound waves – usually travel faster in liquids & solids than in gases  Light waves – travel more slowly in liquids & solids than in gases or in empty space  Speed = (frequency)(wavelength)  V = f  Sample Problem: What is the speed of a sound wave that has a wavelength of 2.00m & a frequency of 170.5Hz?

 1) A wave traveling in water has a frequency of 500.0Hz & a wavelength of 3.0m. What is the speed of the wave?  2) The lowest pitched sounds humans can hear have a frequency of 20.0Hz. What is the wavelength of these sound waves if their wave speed is 340.0m/s?  3) The highest pitched sounds humans hear have a wavelength of 0.017m in air. What is the frequency of these sound waves if their wave speed is 340.0m/s?

Answers  1) v = frequency x wavelength (500Hz)(3m) (500Hz)(3m) 1,500m/s 1,500m/s 2) Wavelength = speed / frequency 340m/s / 20Hz 340m/s / 20Hz 17m 17m 3) Frequency = speed / wavelength 340m/s / 0.017m 340m/s / 0.017m 20,000Hz 20,000Hz