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  • Waves

    1. 1. Waves
    2. 2. What is a wave? <ul><li>Disturbance that travels from one location to another location </li></ul><ul><li>Wiggle in time </li></ul><ul><li>Transfer of energy from one place to another </li></ul><ul><li>Excitement of molecules in which particle move, but are not transported </li></ul><ul><li>You make up your own…… </li></ul>
    3. 3. Types of waves <ul><li>Mechanical – requires a medium for the transfer of energy </li></ul><ul><ul><li>Two types – longitudinal and transverse </li></ul></ul><ul><li>Electromagnetic – do not require medium to travel. They can travel through a vacuum. </li></ul><ul><ul><li>All EM radiation travels at the “speed of light” </li></ul></ul><ul><ul><li>300,000,000 m/s, or 670,000,000 mph, 186,000 miles per second </li></ul></ul>
    4. 4. Wave Words <ul><li>Medium – substance or material which carries the wave </li></ul><ul><ul><li>Medium will affect the speed of the wave </li></ul></ul><ul><ul><li>Air, water, land, rock, string, metal </li></ul></ul><ul><ul><li>Speed of sound in: air 343 m/s, water 1482 m/s steel 5960 m/s </li></ul></ul>
    5. 5. More Wave Words <ul><li>Crest – section of the wave that rises above the undisturbed position </li></ul><ul><li>Trough – section of the waves that dips below the undisturbed position </li></ul><ul><li>Amplitude – maximum displacement of medium above the undisturbed position </li></ul><ul><li>Wavelength – distance between two adjacent corresponding location on the wave (measure in meters) </li></ul>
    6. 6. Even more Wave Words <ul><li>Frequency – the number of waves which pass by in a given amount of time (measured in Hertz, cycles per second) </li></ul><ul><li>Period – amount of time it takes for one wave to pass (measure in seconds) </li></ul>
    7. 7. Still more Wave Words <ul><li>Rarefaction – area of low pressure in a longitudinal wave </li></ul><ul><ul><li>When molecules are most spread out </li></ul></ul><ul><li>Compression – area of high pressure in a longitudinal wave </li></ul><ul><ul><li>When molecules are packed close together </li></ul></ul>
    8. 8. Transverse Wave <ul><li>Particle move perpendicular (up and down) to motion of the energy </li></ul><ul><li>Examples: ocean waves, S-waves, stadium “wave” </li></ul>
    9. 9. Parts of a Transverse Wave
    10. 11. San Andreas Fault
    11. 12. Earthquake Body Waves <ul><li>Primary “P” Waves </li></ul><ul><li>Longitudinal waves </li></ul><ul><li>Travel through liquid, solid or gas </li></ul><ul><li>Fastest EQ waves </li></ul><ul><ul><li>1.5 – 8 km/s </li></ul></ul><ul><li>Some animals can hear them, we feel them </li></ul><ul><li>Not as destructive </li></ul><ul><li>Shear “S” Waves </li></ul><ul><li>Transverse waves </li></ul><ul><li>Travel through solids only </li></ul><ul><li>Slower than P-waves </li></ul><ul><li>Tell us the mantle is molten (liquid) </li></ul>
    12. 13. Seismograph –instrument which records the magnitude of an earthquake Seismogram - – data or graph collected by the seismograph [seismograph (graph) and seismometer (instrument) are also used and becomng the norm]
    13. 14. <ul><li>Logarithmic scale used to measure the magnitude of an earthquake </li></ul><ul><ul><li>4.0 is 10x stronger than 3.0 </li></ul></ul><ul><li>Microquake – less than 2.0, undetected by humans </li></ul><ul><li>Moderate quakes are less than 6.0 </li></ul><ul><li>Greatest recorded earthquake was 8.9 </li></ul><ul><ul><li>12/26/2004 </li></ul></ul>Richter Scale
    14. 16. <ul><li>1990 – 6.2 on Ritcher Scale </li></ul><ul><li>Occurred at subduction zone </li></ul><ul><li>Sound is speeded up 50x </li></ul><ul><li>Actual earthquake was 20 seconds </li></ul><ul><li>Hear sharp P-waves first followed by louder S-waves </li></ul>Hear an Earthquake in New Zealand
    15. 17. Longitudinal Waves <ul><li>Particle movement is parallel (back and forth) compared to direction of energy motion </li></ul><ul><li>Examples: Sound waves, P - waves </li></ul>
    16. 23. <ul><li>Compare types of waves </li></ul><ul><li>http://www.gmi.edu/~drussell/Demos/waves/wavemotion.html </li></ul><ul><li>Play with frequency, amplitude </li></ul><ul><li>http://surendranath.tripod.com/Applets/Waves/Twave01/Twave01Applet.html </li></ul>