NOTE: To change the image on this slide, select the picture and delete it. Then click the Pictures icon in the placeholder to insert your own image. 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 90 o 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 NOVA: Deadliest Earthquakes