Waves Chapter 15 Section 2

Objectives  What are ways to measure and compare waves  How can you calculate speed of a wave?

How Do Waves Move Particles  Transverse waves: the particles in the medium move perpendicular to the direction the wave is traveling.  Example: Ocean waves  Longitudinal waves: particles in the medium vibrate parallel to the direction in which the wave moves.  Example: sound waves, slinky

How Do Waves Move Particles  When a mechanical wave travels through a medium, the particles in the medium vibrate.  Different kinds of mediums cause the wave to vibrate in different ways  This is how scientists classify waves: by how they cause particles to move

Characteristics of Waves

Crest and Trough  The high points in transverse waves are called crests.  The low points in transverse waves are called troughs.

Compression and Rarefractions  Longitudinal waves do not have crests and troughs, instead they have compressions and rarefactions.  Compressions are where particles are close together.  Rarefractions are where the particles are farther apart.

Amplitude  Amplitude is the largest distance that a wave displaces particles from their resting positions.  In transverse waves it is the distance between the resting position and the wave’s crest or trough.

Wavelength  In transverse waves the distance between one crest and the next, or one trough and the next.  In longitudinal waves, the wavelength is the distance between two neighboring compressions or refractions.

Period  Period is the time it takes for one full wavelength of the wave to pass a specific point. Meaning the time it takes for a crest and trough to pass.  Period is represented as a T in equations and its units are units for time, such as seconds

Frequency  Frequency is the number of wavelengths that pass you in a specific amount of time.  The symbol for frequency is f.  The SI unit for frequency is a Hertz or Hz  Frequency = 1/ period

Wavelength speed  How do we calculate wavelength speed?  The speed of a wave is the time it takes for one part of the wave to travel a certain distance.  Speed = wavelength/period or Speed = wavelength x frequency

Calculating Speed of a wave  A piano string vibrates to produce a note. The sound waves the string produce have a frequency of 262 Hz and a wavelength of 1.30m. What is the speed of the sound waves?

Answer  Speed= wavelength x frequency  Speed= 1.30m x 262 Hz  Speed = 341 m/s

Describing Waves

Great Websites  ves/partsOfAWave/waveParts. ves/partsOfAWave/waveParts. ves/partsOfAWave/waveParts.