WAVES
Unit 6
THE NATURE OF WAVES
Chapter 10
Section 1, Section 2
Waves Are Everywhere
 Waves are everywhere:
 Microwaves heating your food
 Ocean waves
 Sound waves
 Light waves
 Can you think of more examples?
Waves
 A wave is a repeating disturbance or movement that
transfers energy through matter or space
 Waves transfer energy
 Waves do not transfer matter
 The particles of the matter are only temporarily displaced
 A force acting upon the particles restores them to their original
position
 The particles of the medium simply vibrate about a fixed position
as the pattern of the disturbance moves from one location to
another location
Types of Waves
 Mechanical Waves
 Waves that can only travel through a medium
 Medium is matter a wave travels through
 The medium can be solid, liquid, gas, or a combination of
the these
 There are two types of mechanical waves:
 Transverse waves
 Compressional waves
Mechanical Waves
 Transverse Waves
 Matter moves back and forth at a 90o angle to the
direction the wave it travelling
Transverse Waves
Mechanical Waves
 Compressional Waves
 Also called Longitudinal Waves
 Matter moves back and forth in the same direction the
wave it travelling
Compressional Waves
Parts of a Wave
 Transverse waves have alternating high points and low point
 High pointscrests
 Low pointstroughs
 Compressional waves have tighter compression and looser
compression
 Tight compressioncompression
 Lower compressionrarefaction
Properties of a Wave
 All waves have a property called wavelength
 Wavelength is the distance between one point on a wave
and the nearest point just like it




Crest to Crest
Trough to Trough (b)
Compression to Compression (a)
Rarefaction to Rarefaction
Properties of Waves
 Frequency
 Number of wavelengths that pass a fixed point each second
 Frequency is expressed in Hertz (Hz)
 A frequency of 1 Hz means one wavelength passes a fixed point
every second
 What does 100 Hz mean?
 100 wavelength pass a fixed point every 1 second
 As frequency increases, wavelength decreases.
Properties of Waves
 Period
 Amount of time it take for one wavelength to pass a point
 As frequency increases, period decreases.
 Period is measured in seconds
Properties of Waves
 Wave Speed
 Speed of a wave depends on the medium it’s travelling through
 Sound waves usually travel faster in liquid and solids than gases
 Light waves travel faster in gas or empty space
 Wave speed can be calculated by the following equation:
Properties of Waves
 Amplitude
 Related to the energy
transferred by a wave
 For a compression wave
 High amplitude waves
 Tighter compressions
(more dense)
 For a transverse wave
 High amplitude waves
 Taller peaks
Water Waves
 Water waves are not purely transverse waves
 Water waves also have some longitudinal motion
 The result is particles of water following a circular motion
pattern
 Objects floating on the surface of water will also bob in a
circular motion
Water Waves
How Are Water Waves Formed
 Wind causes ripples to form on the surface of the water
 With energy of the wind is being transferred to the surface
of the wind
 The waves will depend on the length of time and the
distance over which the wind blows as well as the wind
speed
Ocean Waves
Seismic Waves
 When a guitar spring breaks, it vibrates for a short time and
produces sound waves
 When the Earth’s crust shifts, bends, or breaks, the crust
vibrates creating seismic waves
 Seismic waves are also combinations of compressional and
transverse waves
 When objects on the Earth’s surface absorb some of the
energy in seismic waves, they move and shake causing an
earthquake
Earthquakes
Deadliest Earthquakes Video
 NOVA: Deadliest Earthquakes