Intro to waves

Intro to waves

1. transverse waves

   • A transverse wave is   wave in which the matter in the medium moves at right angles to the direction of the wave, has crests and troughs. 

2. longitudinal waves

   •  a wave in which the matter in the medium moves back and forth along the direction that the wave travels
   • Rarefaction - less dense region of a longitudinal wave
   • compression - dense region of a longitudinal wave

3. IMPORTANT TERMS

   • wavelength
     •   distance between one point on a wave and the next point just like it. ex. crest - crest, trough - trough or compression - compression, rarefaction - rarefaction   
   • frequency
     •  the number of wavelengths that pass a fixed point each second; is expressed in hertz (Hz) 
     • For a wave to have a frequency of one hertz it has to have one wavelength pass a fixed point in 1 second 
   • period
     • the amount of time it takes one wavelength to pass a fixed point 
   • resonance
     • the process by which an object is made to vibrate by absorbing energy at its natural frequencies.   
     • EX. tuning fork and a women singing at an opera and hits a note that has the same frequency as a glass bottle it will crack 
   • amplitude
     •  a measure of the size of the disturbance of a wave, related to the energy that it carries. 
   • refraction
     • the bending of a wave caused by a change in its speed as it travels through different mediums 
     •  EX.   When light enters water it slows down, causing it to bend toward the normal 
     • EX.     When light goes from water to light it SPEEDS UP and it bends away from the normal 
   • diffraction
     • bending of a wave around an object 
   • interference
     • the process of two or more waves overlapping, and combining to form a new wave
     • Destructive Interference = happens when a crest meets a trough of another wave ( subtraction ) 
     • Constructive Interference = crests overlap w/ crests ( adding ) 
   • standing wave
     • waves of equal wavelength and amplitude, but traveling in opposite directions, continuously interfere with each other; does not appear to be traveling.
     • nodes = locations where the interfering waves always cancel 
     • ex. when the string of a violin is played with  bow it vibrates and creates standing waves 
   • REFLECTION
     • when light bounces of an object
     • EX. Light strikes a mirror and then the light is reflected off onto your face the back to the mirror allowing you to see yourself. 

4. Mechanical Waves

   • a wave that has to have a medium to move 
   • not all waves are mechanical light and radio waves travel through a vacum 
   • Seismic Waves
     • both compressional ( on surface ) and transverse ( under ground ) 
     • Mechanical b/c they use the medium of ROCKS 
   • Sound waves
     • Use the medium of air 
   • Water waves
     • Use the medium of water