Ch 18 Waves Sound I Characteristics of Waves

Ch. 18 - Waves & Sound I. Characteristics of Waves Ø Transverse waves Ø Longitudinal waves Ø Measuring waves

A. Waves Ø Waves w rhythmic disturbances that carry energy through matter or space Ø Medium w material through which a wave transfers energy w solid, liquid, gas, or combination w electromagnetic waves don’t need a medium (e. g. visible light)

A. Waves ØTwo Types: Longitudinal Transverse

B. Transverse Waves ØTransverse Waves w medium moves perpendicular to the direction of wave motion

B. Transverse Waves ØWave Anatomy wavelength crest corresponds to the amount of energy carried by the wave amplitude nodes trough wavelength

C. Longitudinal Waves ØLongitudinal Waves (a. k. a. compressional) w medium moves in the same direction as wave motion

C. Longitudinal Waves ØWave Anatomy compression rarefaction wavelength Amount of compression corresponds to amount of energy AMPLITUDE.

D. Measuring Waves ØFrequency ( f ) w # of waves passing a point in 1 second w Hertz (Hz) w shorter wavelength higher frequency higher energy 1 second

D. Measuring Waves ØPeriod w Amount of time it takes for one cycle w Measured in Seconds w T = 1/f or f=1/T • T = Period

D. Measuring Waves ØVelocity ( v ) w speed of a wave as it moves forward w depends on wave type and medium v= ×f v: velocity (m/s) : wavelength (m) f: frequency (Hz)

D. Measuring Waves Ø EX: Find the velocity of a wave in a wave pool if its wavelength is 3. 2 m and its frequency is 0. 60 Hz. WORK: v= ×f GIVEN: v=? = 3. 2 m f = 0. 60 Hz v = (3. 2 m)(0. 60 Hz) v v = 1. 92 m/s f

D. Measuring Waves Ø EX: An earthquake produces a wave that has a wavelength of 417 m and travels at 5000 m/s. What is its frequency? WORK: f=v÷ GIVEN: = 417 m v = 5000 m/s f=? v f = (5000 m/s) ÷ (417 m) f = 12 Hz f