WAVES

WAVES  Carries energy from one place to another  Classified by what they move through 1. Mechanical Waves the energy is transferred by vibrations of medium (medium = matter) ex/ ocean waves move through water 2. Electromagnetic waves (EM Waves) the energy moves through disturbances in the electromagnetic field. No medium necessary. a disturbance that transfers energy

MECHANICAL WAVES Classified by how medium vibrates Longitudinal Waves: Vibration is in the same direction as wave pulse (parallel to wave pulse) Ex: sound, some earthquake waves Transverse Waves: Vibration is at 90 0 (right angles) to wave pulse Ex: light, some earthquake waves Surface Waves: Vibration is circular Ex: Ocean waves; surface waves

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

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” Distance between “rest & crest” or “rest & trough” Gives indication of “power” or “strength” of wave (magnitude of earthquake = Richter scale) Gives indication of “power” or “strength” of wave (magnitude of earthquake = Richter scale) Determines loudness Determines loudness (sound) or brightness (EM wave) (EM wave)

WAVELENGTH 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

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

LONGITUDINAL WAVES  Back and forth (compression & rarefraction)  Also called compression or pressure wave  Wavelength is from compression to compression or rarefaction to rarefaction or rarefaction to rarefaction Vibration is parallel to the direction of the motion of the wave Rarefraction (expansion) Compression

VELOCITY v  the rate at which the energy travels; speed & direction  Depends on medium Mechanical waves travel faster through dense mediums Mechanical waves travel faster through dense mediums EM Waves are faster through less dense mediums EM Waves are faster through less dense mediums If same medium, which is faster?

What can Sound waves do?  Waves can reflect (bounce) Echoes  Waves can refract (bend) Slight amplifications (mostly over water)

What can Sound waves do?  Waves can diffract (scatter) Ability to hear around corners, through doors, etc.

The Doppler Effect

The Doppler Effect Applications For Light For Sound For Water

Properties of Sound  Loudness controlled by amplitude (dB)  Pitch controlled by frequency (Hz)  Speed controlled by medium