WAVES

1
WAVES
2
WAVES
a disturbance that transfers energy

• Carries energy from one place to another
• Classified by what they move through
• Mechanical Wavesthe energy is transferred by
  vibrations of medium (medium matter)ex/ ocean
  waves move through water
• Electromagnetic waves (EM Waves)the energy moves
  through disturbances in the electromagnetic
  field.

3
WAVE STRUCTURE
CREST (peak)
AMPLITUDEresting to max peak
WAVELENGTH
TROUGH
4
MECHANICAL WAVES
require a medium (the material through which the
disturbance is moving) to transmit energy

• travel through gradually lose energy to that
  medium
• Examples
• water, sound, rope, spring waves
• Mechanical Media
• water, air, rope, spring

5
MECHANICAL WAVES


           

           
Classified by how medium vibrates
Pulse direction of energy transfer
Vibration direction of vibration of medium
relative to pulse
3 types
6
MECHANICAL WAVES
Classified by how medium vibrates
Longitudinal Waves Vibration is in the same
direction as wave pulse (parallel to wave pulse)
Transverse Waves Vibration is at 900 (right
angles) to wave pulse
Surface Waves Vibration is circular Ex/ Ocean
waves surface waves
7
TRANVERSE WAVES


           
Vibration is perpendicular to the direction of
the motion of the wave

• Sideways or up down
• Examples
• S-type earthquake waves
• Electromagnetic (EM) or light waves

8
LONGITUDINAL WAVES
Vibration is parallel to the direction of the
motion of the wave

• Back and forth (compression rarefraction)
• Also called compression or pressure wave
• Examples
• P-type earthquake waves
• Sound waves

9
Waves describe the Earth
P waves move through solids liquids
P waves move through solids liquids
S waves move through solids only!!!
Are these MECHANICAL WAVES???? YES!!
Seismic waves need a medium (the earth!)
10
CHARACTERISTICS OF WAVES

• Waves are described according to their
• Amplitudemeasures DISPLACEMENTsize of the
  disturbance
• Wavelength ? distance of a repeating
  unitAlso called a cycle
• Velocity v speed how fast wave travels

11
AMPLITUDE

• Distance between rest crest or rest
  trough
• Gives indication of power or strength of
  wave(magnitude of earthquake Richter scale)
• Does not affect velocity of wave
• Determines loudness (sound) or brightness (EM
  wave)

12
WAVELENGTH ?

• Distance between any two repeating points on a
  wavecrest-crest, trough-trough,expansion-expan
  sion, compression-compression
• Determines what colorswe see what notes we hear
  (pitch)
• Shorter wavelengths have more cycles per minute
  because they arent as long

13
VELOCITY v

• the rate at which the energy travels speed
  direction
• Depends on medium
• Mechanical waves travel faster through dense
  mediums
• EM Waves are faster through less dense mediums

14
Frequency ƒ

• How often number of wavelengths that pass any
  point per second

• measured in wavelengths/second or
  cycles/secondHertz (Hz) number of
  wavelengths in 1 second
• Frequency is related to velocity v ƒ ?

15
PERIOD T

• How longAmount of time for one wavelength to
  pass a point
• Related inversely to frequency

Period 1 Frequency
1 1T f
16
Internet resources
http//www.glenbrook.k12.il.us/gbssci/Phys/Class/
waves/wavestoc.html
To test how well you understand go to
http//www.physicsclassroom.com/Class/waves/u10l1
c.cfmemmech