WAVES

WAVES a disturbance that transfers energy Carries energy from one place to another Classified by what they move through 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. Physics The act or process of propagating, especially the process by which a disturbance, such as the motion of electromagnetic or sound waves, is transmitted through a medium such as air or water. A medium is a substance or material which carries the wave

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 Examples: water, sound, rope, & spring waves Mechanical Media: water, air, rope, spring Making a pulse

MECHANICAL WAVES Classified by how medium vibrates                         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 Sideways or up & down Examples:             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

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 Rarefraction (expansion) Compression

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!)

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

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)

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

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

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

PERIOD T How long Amount of time for one wavelength to pass a point Related inversely to frequency Period = 1 Frequency When an event occurs repeatedly, then we say that the event is periodic and refer to the time for the event to repeat itself as the period. 1 = 1 T f

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/u10l1c.cfm#emmech When an event occurs repeatedly, then we say that the event is periodic and refer to the time for the event to repeat itself as the period.