Waves transmit energy through matter and space without actually transporting matter. There are different types of waves including transverse waves, longitudinal waves, and surface waves. The key properties of waves are amplitude, wavelength, frequency, and velocity. Waves can interact through reflection, refraction, diffraction, and interference. Interference from standing waves caused the catastrophic collapse of the Tacoma Narrows Bridge in 1940.

1. Chapter 20: The Energy of Waves

3. Animation courtesy of Dr. Dan Russell, Kettering University

4. What is a wave? (Besides at a ballgame…lol) Any disturbance that transmits energy through matter or space Where are they? a. in the ocean b. microwave ovens c. light waves from the sun d. sound waves e. radio waves

5. What do waves carry? ENERGY!!! Waves do not move particles.

6. Some waves need help to travel… A medium is a substance through which a wave can travel. A medium can be a solid, liquid, or gas. What waves need a medium? a. sound b. ocean waves What are these waves called that require a medium? Mechanical Wave Waves that do not require a medium are called electromagnetic waves.

7. How waves travel: Transverse: particles move up and down perpendicular to direction of the wave Longitudinal Waves (also called Compressional Waves): particles vibrate back and forth along the path of the wave travels Surface Waves: combination of transverse and longitudinal waves

8. Section 2:Properties of Waves

9. B. Transverse Waves Wave Anatomy corresponds to the amount of energy carried by the wave crests troughs wavelength wavelength amplitude amplitude nodes

10. C. Longitudinal Waves Wave Anatomy Amount of compression corresponds to amount of energy  AMPLITUDE. rarefaction compression wavelength wavelength

11. Longitudinal Wave Compression - dense regions- like the crest of a transverse wave Rarefaction- less dense regions- like the trough of a transverse wave

12. Properties of Waves Amplitude: maximum wave height from the rest position; larger amplitude = more energy Wavelength: distance between crest to crest or trough to trough; compression to compression or rarefaction to rarefaction

13. Waves The more energy a wave carries, the greater its amplitude High amplitude in compressional waves means that medium is pushed together more at the compressions High amplitude in transverse waves means taller crests and deeper troughs http://www.sfu.ca/sonic-studio/handbook/Amplitude.html http://id.mind.net/~zona/mstm/physics/waves/introduction/introductionWaves.html

14. Waves The amplitude of compressional waves is related to how tightly the medium is pushed together at compression Denser compressions = larger amplitude = more energy Less dense rarefactions = lower amplitude = LESS energy

15. Properties of Waves… Frequency: the number of waves produced in a given amount of time; measured in hertz (Hz); 1 Hz = 1 wave per second (1 Hz = 1/s); higher frequency means higher energy Period: the time it takes for a complete vibration

16. D. Measuring Waves Velocity ( v ) speed of a wave as it moves forward depends on wave type and medium v =  × f v : velocity (m/s)  : wavelength (m) f : frequency (Hz)

17. D. Measuring Waves EX : Find the velocity of a wave in a wave pool if its wavelength is 3.2 m and its frequency is 0.60 Hz. WORK: v =  × f v = (3.2 m)(0.60 Hz) v = 1.92 m/s GIVEN: v = ?  = 3.2 m f = 0.60 Hz  v f

18. D. Measuring Waves EX : An earthquake produces a wave that has a wavelength of 417 m and travels at 5000 m/s. What is its frequency? WORK: f = v ÷  f = (5000 m/s) ÷ (417 m) f = 12 Hz GIVEN:  = 417 m v = 5000 m/s f = ?  v f

19. Waves Light waves travel faster in gases and vacuums than in liquids and solids Radiation moves faster when particles are not in the way Why are some earthquakes very damaging and other barely felt? Depends on the energy of the wave.

20. Waves Amplitude of transverse waves Distance from crest or trough of a wave to the rest position of the medium Higher ocean waves = more energy!

21. Breaking a glass with sound- resonance: http://www.teachersdomain.org/resources/lsps07/sci/phys/energy/glassbreak/index.html Sound from sand dunes: http://www.teachersdomain.org/resources/hew06/sci/phys/maf/boomsand/index.html Light as particles: http://www.teachersdomain.org/resources/phy03/sci/phys/fund/uncertainty/index.html

22. Wave Interactions

23. Wave Interactions… Reflection Reflection : occurs when a wave bounces back after striking a barrier All waves can be reflected. Reflected sound waves are called echoes . Sunlight is being reflected off of the moon at night. Water waves reflect off a shoreline.

24. More wave interactions… Refraction is the bending of a wave as it passes at an angle from one medium to another. Speed of refraction depends on the medium.

25. Wave interactions… Diffraction: the bending of waves around or through an opening; diffraction depends on wavelength and the size of barrier/opening

26. Last wave interaction… Interference : the result of 2 or more waves overlapping. a. constructive interference : increases the amplitude of a wave b. destructive interference : decreases the amplitude of a wave Great diagram of waves http://www.sciencejoywagon.com/physicszone/09waves/

27. More on interference waves Can create standing waves Standing wave is a wave that forms a stationary pattern in which portions of the wave are at the rest position. Standing waves have nodes and antinodes.

28. Standing Waves

29. Interference Waves can be deadly! July 1, 1940- Tacoma Bridge Accident