2. Chapter 19 Vibrations and Waves

3. There are two ways to transmit information/energy in our universe: Particle Motion and Wave Motion

4. Light and Sound Both are vibrations of different kinds Vibration -mechanical oscillations about an equilibrium point disturbance that travels through space and time Wave -

5. 1.VIBRATION OF A PENDULUM Demo - Metronome Demo - Bowling ball pendulum Java Demo n What does the period (T) depend upon?  Length of the pendulum ( l ). u Acceleration due to gravity (g). n Period does not depend upon the bob mass or the amplitude of the swing.

6. Video - Swinging ExamplesSwinging Examples Demo - Pendulum with extra mass

7.  Pendulum Uses: Timing Oil prospecting Walking When oscillations are small, the motion is called simple harmonic motion (shm) and can be described by a simple sine curve.

8. 2.WAVE DESCRIPTION Picture of a Transverse Wave Wavelength A - Amplitude A Crest Trough

9. Wavelength ( ) Distance between adjacent crests in a transverse wave Distance a wave travels during one vibration Units - meters or feet

10.  Time required to make one vibration. Time required to generate one wave. Time required for the wave to travel one wavelength. Period (  )

11. Frequency (f) The number of vibrations per unit of time made by the vibrating source. Units - cycles per second 1/s Hertz (Hz)

12. Examples of Frequency What is the frequency of the second hand of a clock? Frequency = 1cycle/60 secPeriod = 60 sec What is the frequency of US Presidential elections? Frequency = 1 election/4 yrsPeriod = 4 yrs

13. In symbolic form or

14. 3.WAVE MOTION Energy is transported by particles or waves. A wave is a disturbance transmitted through a medium. Exception: light does not require a medium.

15. n medium - the stuff that carries the wave Waves Medium water waves water waves on a rope rope stadium waves people sound air light space (vacuum) Wave Motion

16. 4.WAVE SPEED The average speed is defined as

17. For a wave, if the distance traveled is a wavelength ( ), then the time to travel this distance is the period (T). Thus or

18. is true for all waves. Note: v is dictated by the medium. (must change medium to change v) f is dictated by the source. (must change the source to change f ) Demo - Complete Bell Wave Machine

19. 5.TRANSVERSE WAVES URLURL – Transverse Waves Video - Slinky Transverse Waves Examples: string musical instruments ripples on water electromagnetic waves

20. A disturbance moves through the medium. Elements of the medium vibrate. Examples: ripples on water wheat waves

21. 6.LONGITUDINAL WAVES URLURL – Longitudinal Waves Video - Slinky Longitudinal Waves Rarefactions Compressions

22. Demo - Slinky Example: sound in air

23. 7.INTERFERENCE Collision of Pulses Superposition of Waves Overhead - Interference Interference is a characteristic of all waves.

24. Two Slit Interference Constructive and Destructive Interference

25. Standing Waves When two sets of waves of equal amplitude and wavelength pass through each other in opposite directions, it is possible to create an interference pattern that looks like a wave that is “standing still.” Demo - Rope and strobe URL – Standing Waves URL

26. Standing Waves

27. Notes on Standing Waves There is maximum vibration at an antinode.  is twice the distance between successive nodes or successive antinodes. There is no vibration at a node.

28. Demo - Soda straw wave machine Demo - Organ pipe and tuning fork Another example: musical instruments URL - Drumhead VibrationsDrumhead Vibrations Wave Examples

29. 8.DOPPLER EFFECT Refers to the change in frequency when there is relative motion between an observer of waves and the source of the waves Doppler with Sound n Doppler with Water Doppler with Water

30. Barrier and Bow Waves Barrier Wave - a wave source moving to the right at a speed equal to the wave speed Bow Wave - wave source moving to the right at a speed in excess of the wave speed

31. 10.SHOCK WAVES There are two booms, one from the front of the flying object and one from the back. Supersonic jet The boom is not produced just when the flying object “breaks” through the sound barrier.

32. Supersonic

33. Doppler Effect Notes Motion of SourceSound Light and Observer Moving togetherHigher“Blue Shift” Pitch Moving ApartLower“Red Shift” Pitch

34. Doppler Shift Gives Radial Velocity Radar True Velocity Tangential Velocity Radial Velocity

36. n Demo - Crack whip

37. Supersonic - faster than the speed of sound n Mach Number = speed of sound speed of object Subsonic – slower than the speed of sound

38. Chapter 19 Review Questions

39. Doubling the mass of a simple pendulum undergoing small oscillations does what to the period of the pendulum? (a) cuts it in half (b) increases it by the square of 2 (c) nothing (d) doubles it (c) nothing

40. What dictates the frequency of a sound wave? (a) wavelength (b) medium (c) source of the sound (d) speed (e) amplitude (c) source of the sound

41. What determines the speed of a wave? (a) the frequency (b) the wavelength (c) the amplitude (d) the period (e) the medium of transmission

42. A skipper on a boat notices wave crests passing his anchor chain every 5 seconds. If the wave crests are 15 m apart, what is the speed of the water waves in m/s? (a) 5 (d) 10 (b) 15 (e) 3 (c) 75 (e) 3

43. For a medium transmitting a longitudinal wave, the areas of the medium where the density of the medium is temporarily increased are called... (a) rarefactions (b) compressions (c) density holes (b) compressions

44. When you move away from a fixed source of sound, the frequency of the sound you hear... (a) is greater than what the source emits (b) is less than what the source emits (c) is the same as what the source emits (b) is less than what the source emits

45. Sonic booms from a plane are produced... (a) because the plane breaks through the sound barrier. (b) when the plane reaches the speed of sound. (c) by the plane traveling faster than the speed of sound. (d) by the plane traveling slower than the speed of sound. (c) by the plane traveling faster than the speed of sound