WAVES WAVES a disturbance that transfers energy Carries

WAVES

WAVES a disturbance that transfers energy Carries energy from one place to another Ø Classified by what they move through Ø 1. 2. Mechanical Waves the 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.

WAVE STRUCTURE CREST (peak) AMPLITUDE resting to max peak WAVELENGTH TROUGH

MECHANICAL WAVES require a medium (the material through which the disturbance is moving) to transmit energy travel through & gradually lose energy to that medium Ø Examples: l Ø water, sound, rope, & spring waves Mechanical Media: l water, air, rope, spring Making a pulse WATCH THE VIDEO!!! https: //www. youtube. com/watch? v=-k 2 Tu. Jf. NQ 9 s

MECHANICAL WAVES Classified by how medium vibrates Pulse = direction of energy transfer Vibration = direction of vibration of medium relative to pulse 3 types: Longitudinal, transverse, surface

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

TRANVERSE WAVES Vibration is perpendicular to the direction of the motion of the wave Sideways or up & down Ø Examples: Ø l l S-type earthquake waves Electromagnetic (EM) or light waves

LONGITUDINAL WAVES Vibration is parallel to the direction of the motion of the wave Ø Back and forth (compression & rarefraction) Ø Also called compression or pressure wave Ø Examples: l P-type earthquake waves l Sound waves Rarefraction (expansion) Compression

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

CHARACTERISTICS OF WAVES Waves are described according to their Ø Amplitude measures DISPLACEMENT size of the disturbance Ø Wavelength distance of a “repeating unit” Also called a cycle Ø Velocity v speed = how fast wave travels

AMPLITUDE l l Distance between “rest & crest” or “rest & trough” Gives indication of “power” or “strength” of wave (magnitude of earthquake = Richter scale) l l Does not affect velocity of wave Determines loudness (sound) or brightness (EM wave)

WAVELENGTH Ø Distance between any two repeating points on a wave crest-crest, trough-trough, expansion-expansion, compression-compression Ø Determines what colors we see; what notes we hear (pitch) Ø Shorter wavelengths have more cycles per minute because they aren’t as long

VELOCITY v Ø the rate at which the energy travels; speed & direction Ø Depends on medium l l Mechanical waves travel faster through dense mediums EM Waves are faster through less dense mediums

Frequency ƒ Ø How often number of wavelengths that pass any point per second Ø measured in wavelengths/second or cycles/second Hertz (Hz) = number of wavelengths in 1 second Ø Frequency is related to velocity: v = ƒ

PERIOD T Ø How long Amount of time for one wavelength to pass a point Ø Related inversely to frequency Period = 1 Frequency 1 = 1 T f

Internet resources http: //www. glenbrook. k 12. il. us/gbssci/Phys/Class/wavestoc. html To test how well you understand go to http: //www. physicsclassroom. com/Class/waves/u 10 l 1 c. cfm#emmech