1. WAVES

2. Waves A wave is any disturbance that transmits ENERGY through matter and space. Waves carry energy NOT matter. SIM

3. Kinds of Waves –Longitudinal Wave The material that the wave is in vibrates back and forth along the path that the wave travels. SIM

4. Kinds of Waves –Transverse Wave The material that the wave is in moves perpendicular (at right angles) to the direction that the wave is traveling. SIM

6. Longitudinal Waves Compression –Section of a longitudinal wave where the particles are crowded together Rarefaction –Section of a longitudinal wave where the particles are less crowded than normal

7. SIM

8. Transverse Waves Crests –The highest point in a transverse wave. Troughs –The lowest point in a transverse wave. SIM

9. Crest and Trough

10. Amplitude –Maximum distance the wave vibrates from its rest position SIM

11. Which one of these waves has a larger amplitude?

12. Wavelength Wavelength (λ) –The distance from any point on one wave to that same point on the next wave SIM SIM2 λ λ

13. The wavelength of a longitudinal wave can be measured as the distance between the center of two compressions or rarefactions.

14. Which one of these waves has a larger wavelength ( λ) ?

15. Frequency –The number of waves (or cycles) produced in a given amount of time SIM

16. Which one of these waves has a higher frequency?

17. Review

18. Reflection –When a wave bounces back after striking a barrier SIM SIM2

19. Refraction –The bending of a wave as it passes at an angle from one material (medium) to another. SIM

20. Diffraction –The bending of waves around a barrier or through an opening. SIM SIM2

21. Interference Interference is the result of two or more waves overlapping. Constructive Interference –Occurs when the crests of one wave overlap the crests of another wave OR the troughs of the waves overlap

22. Interference Destructive Interference –Occurs when the crests of one wave and the troughs of another wave overlap

23. Interference SIM

24. Standing Waves Standing wave SIM SIM –A wave that forms a stationary pattern. –Portions of the wave do not move and other portions have a large amplitude –At rest= total destructive interference –Large amplitude=constructive interference.

25. Sound waves are reflected at a boundary. (SIM1) (SIM2)SIM

26. Sound waves are refracted at a boundary.

27. Interference. –Constructive interference –Destructive interference

28. Here’s what is occurring. (SIM1) (SIM2)SIM2 SIM - Interference

29. Multiple sound sources interfere (SIM)SIM Changing separation distance.

30. Multiple sound sources interfere. Changing source frequency.

31. What is a Medium? A substance through which a wave can travel –Water –People –Air –Coiled wire

32. What is a Mechanical Wave? A wave that requires a medium Examples: –Sound –Water

34. Resonance Objects have resonant frequencies An object vibrating at the resonant frequency of a second object causes the second object to vibrate too! SIM - Resonance

35. Speed of Sound Lightening/Thunder SIM

36. What Effects The Speed of Sound? Medium

37. What Effects The Speed of Sound? Temperature As the temperature rises, the sound travels faster! SIM

38. Pitch How high or low you perceive a sound to be Determined by the frequency High Pitch Low Pitch

39. Ultrasonic –Sounds with frequencies that are higher than 20,000 Hz Infrasonic- –Sounds with frequencies that are lower than 20 Hz

40. Volume Decibel (dB) - unit to express volume Exposure to sounds above 85 dB causes hearing loss SIM SIM - dB

41. What is an Ultrasound? Ultrasound Simulation

42. Beat Frequency Two waves with similar frequencies alternate constructive/destructive interference Causes sound to alternate loud and soft SIM

43. Beating Frequency (SIM1) (SIM2)SIMSIM2

44. Beating Frequency AppletBeating Frequency Applet 2 Beating Frequency Applet 3

45. Sound from: A stationary object A moving object (SIM1)SIM (SIM2)SIM2 SIM – Doppler Effect Labeled SIM – Hear Doppler SIM – Doppler/hear police siren SIM – Doppler/see police siren

47. Final Note: Mechanical waves and Electromagnetic Waves are different!

48. Sources: Bloomfield, How Things Work. Krauskopf & Beiser, The Physical Universe. 10 th ed. Tillery, Physical Science. www.physicsclassroom.com www.physicsclassroom.com