Properties of Waves

1. Properties of Waves

2. Anatomy of a Wave • Wave: a disturbance that carries energy through matter or space • Crest: the highest point of a wave • Trough: The lowest point in a wave

3. Wave Length • wavelength: the distance between any two corresponding locations on the wave. • Can be measured from: • crest to next crest • trough to next trough • from the middle of a wave to the middle of the next wave.

4. Amplitude • The height of the wave from its center to either a crest or a trough

5. Wave Period • the amount of time for one wave to pass by a certain point. • Calculate by dividing the amount of time by the number of waves that pass by in that time. • A surfer knows that the wave period is important to a good day of surfing. He watches 20 waves go by in 200 seconds. What is the period of the waves? 10 sec/ wave

6. Wave Speed • How fast a wave moves • Remember that rate= distance / time • For a wave • distance= wavelength • Time= wave period • Practice: • The wavelength of an ocean wave is 10 m and the period of the same wave is 5 seconds. What is the wave speed? 2 m/s

7. Types of Waves • Ocean waves • Sound waves • Seismic waves (Earthquake) • Light waves • Electromagnetic spectrum

8. Ocean Waves • disturbances of water surfaces caused by energy from winds, earthquakes, or volcanic explosions • An example of surface waves (waves forming at the boundary between two different materials) • Most ocean waves at the beach are created by wind Breakers (above) crash to the beach in Myrtle Beach, South Carolina.

9. What actually happens when a wave goes by? • Ocean waves transfer energy rather than actually moving the water along with them. • When wave energy passes through water, the water moves in a circular motion. • Watch the beach ball in the following animation • The beach ball moves in a circle while the energy of the wave moves from left to right

10. What actually happens when a wave goes by? • The circles that the water particles make get smaller with depth • The energy being transmitted decreases with depth • Water particles move in a circular pattern down to a depth of ½ the wavelength

11. What happens when a wave reaches the shore? • Water deeper than ½ the wavelength • the energy of the wave moves forward • the water stays in place. • Wave approaches shore • depth of the water is less than ½ the wavelength • the friction against the ocean floor slows the wave down and shortens its wavelength • The wave breaks and crashes on the shore.

12. Mavericks

13. Mavericks Big Waves

14. Mavericks QoD: 1/30 • How big are the waves at Mavericks? • Are they dangerous? • What causes the waves to get so incredibly big?

15. Why do big waves happen here? • Waves start in the North Pacific during winter storms • If the wind is blowing hard enough in the North Pacific, the waves will have a large amount of energy when they reach California

16. Bathymetry of Mavericks • Mavericks is in the box • Seafloor mapping shows blue as deepest

17. Bathymetry • As waves approach Pillar Point, the center of the wave hits shallow water before the sides • The wave slows down in the center, but not the sides • Because the wave speed is different in the center than the sides, the wave becomes curved • The wave height in the center becomes much larger than the sides because the seafloor is shallower there

19. Mavericks

20. Did you turn in your Article??? • Reasons not to procrastinate… • Technical issues • Technical FAILURES • You might get sick • You might forget • You might run out of time • Your dog might eat your assignment instructions, and then you find out that the article you found got lost in your email, and then on top of that your brother needs help doing his homework, and you have to do a make-up test for Math, and…

21. Sources • http://secoora.org/classroom/waves/fact-sheet/ • http://www.pwssc.org/education/media/ • http://geoinfo.amu.edu.pl/wpk/pe/a/harbbook/c_vi/chap06.html