1. Waves & Sound I. Characteristics of Waves  Waves  Transverse waves  Longitudinal waves  Measuring waves

2. A. Waves  Waves  rhythmic disturbances that carry energy through matter or space  Medium  material through which a wave transfers energy  solid, liquid, gas, or combination  electromagnetic waves don’t need a medium (e.g. visible light)

3. B. Waves & Energy  Waves  Carry energy  Waves are caused by vibrations  Can do work  Move objects  Energy  Waves carry energy  Vibration is a transfer of energy  As waves carry energy the particles in the medium move  the direction of the motion determines the type of wave

4. C. Categories of Waves  Mechanical Waves  Must travel through a medium  Cannot travel through a vacuum  Examples: sound, ocean waves  Electromagnetic Waves  Does not require a medium  Can be transferred through a vacuum  Examples: light, UV rays, Visible light

5. D. Types of Waves  Two Types: Longitudinal Transverse

6. D. Transverse Waves  Transverse Waves  medium vibrates perpendicular to the direction of wave motion  Examples: water waves, electromagnetic waves

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

8. E. Longitudinal Waves  Longitudinal Waves (a.k.a. compressional waves)  medium moves in the same direction as the wave’s motion  Examples: sound waves, springs, slinky

9. E. Longitudinal Waves  Wave Anatomy rarefaction compression wavelength Amount of compression corresponds to amount of energy  AMPLITUDE

10. F. Measuring Waves  Frequency ( f )  # of waves passing a point in 1 second  SI unit: Hertz (Hz)  shorter wavelength  higher frequency  higher energy 1 second

11. 1 Frequency = period ( ) or period = the amount of time for one cycle to do a complete motion Frequency is measured in hertz (Hz). 1Hz = 1 wave per second Cycle second F. Measuring Waves

12.  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)

13. F. Measuring Waves Solid  Molecules are close together so waves travel very quickly. Liquid  Molecules are farther apart but can slide past one another so waves do not travel as fast. Gas  Molecules are very far apart so a molecule has to travel far before it hits another molecule, so waves travel slowest in gases.

14. WORK: v = × f v = (3.2 m)(0.60 Hz) v = 1.92 m/s F. 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. GIVEN: v = ? = 3.2 m f = 0.60 Hz v f

15. WORK: f = v ÷ f = (5000 m/s) ÷ (417 m) f = 12 Hz F. 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? GIVEN: = 417 m v = 5000 m/s f = ? v f

16. Ch. 17 – Waves II. Wave Behavior  Reflection  Refraction  Diffraction  Interference  Constructive Interference  Destructive Interference  Doppler effect

17. A. Wave Interactions  Wave Interaction  When a wave meets an object or another wave.  When a wave passes into another medium  Examples: reflection, diffraction, refraction, interference, resonance

18. A. Reflection  Reflection  when a wave strikes an object and bounces off incident beamreflected beam Normal

19. A. Reflection  When a wave bounces off a surface that is cannot pass through

20. B. Refraction  Refraction  bending of waves when passing from one medium to another  caused by a change in speed slower (more dense)  light bends toward the normal SLOWER FASTER faster (less dense)  light bends away from the normal

21. B. Refraction  The bending of a wave as it enters a new medium at an angle.

22. B. Refraction  Refraction depends on…  speed of light in the medium  wavelength of the light - shorter wavelengths (blue) bend more

23. B. Refraction  Example: View explanation.explanation.

24. C. Diffraction  The bending of a wave as it moves around an obstacle or passes through a narrow opening.

25. C. Diffraction  Diffraction  bending of waves around a barrier  longer wavelengths (red) bend more - opposite of refraction

26. D. Interference  The interaction of two or more waves that combine in a region of overlap

27. D. Interference  Two types of Interference  constructive  brighter light  destructive  dimmer light

28. E/F. Constructive & Destructive Interference  Both are caused by two or more waves interacting, but…  Constructive interference combines the energies of the two waves into a greater amplitude  Destructive interference reduces the energies of the two waves into a smaller amplitude.

29. G. Doppler Effect A change in wave frequency caused by movement of sound source, motion of the listener, or both.

30. Ch. 18 - Waves & Sound III. The Nature of Sound  Speed of Sound  Human hearing  Doppler effect  Seeing with sound

31. A. Speed of Sound  344 m/s in air at 20°C  Depends on:  Type of medium travels better through solids than through liquids can’t travel through a vacuum  Temperature of medium travels faster at higher temperatures

32. B. Human Hearing sound wave vibrates ear drum amplified by bones converted to nerve impulses in cochlea

33. B. Human Hearing  Pitch  highness or lowness of a sound  depends on frequency of sound wave  human range: 20 - 20,000 Hz ultrasonic waves subsonic waves

34. B. Human Hearing  Intensity  volume of sound  depends on energy (amplitude) of sound wave  measured in decibels (dB)

35. B. Human Hearing 70 80 100 110 120 40 18 10 0 DECIBEL SCALE

36. C. Doppler Effect  Doppler Effect  change in wave frequency caused by a moving wave source  moving toward you - pitch sounds higher  moving away from you - pitch sounds lower

37. C. Doppler Effect Stationary sourceMoving sourceSupersonic source same frequency in all directions waves combine to produce a shock wave called a sonic boom higher frequency lower frequency

38. D. Seeing with Sound  Ultrasonic waves - above 20,000 Hz Medical ImagingSONAR “Sound Navigation Ranging”

39. IV. Electromagnetic Radiation (p.528-535)  EM Radiation  EM Spectrum  Types of EM Radiation

40. A. Electromagnetic Radiation  Electromagnetic Radiation  transverse waves produced by the motion of electrically charged particles  does not require a medium  speed in a vacuum = 300,000 km/s  electric and magnetic components are perpendicular

41.  The full range of light B. Electromagnetic Spectrum

42. B. Electromagnetic (EM) Spectrum long low f low energy short high f high energy

43. C. Types of EM Radiation  Rabbits Meet In Very Unusual Xciting Gardens

44. C. Types of EM Radiation  Radio waves  Lowest energy EM radiation  FM - frequency modulation  AM - amplitude modulation  Microwaves  penetrate food and vibrate water & fat molecules to produce thermal energy

45. C. Types of EM Radiation  Infrared Radiation (IR)  slightly lower energy than visible light  can raise the thermal energy of objects  thermogram - image made by detecting IR radiation

46. C. Types of EM Radiation  Visible Light  small part of the spectrum we can see  ROY G. BIV - colors in order of increasing energy ROYG.BIV redorangeyellowgreenblueindigoviolet

47. C. Types of EM Radiation  Ultraviolet Radiation (UV)  slightly higher energy than visible light  Types: UVA - tanning, wrinkles UVB - sunburn, cancer UVC - most harmful, sterilization

48. C. Types of EM Radiation  Ultraviolet Radiation (UV)  Ozone layer depletion = UV exposure!

49. C. Types of EM Radiation  X rays  higher energy than UV  can penetrate soft tissue, but not bones

50. C. Types of EM Radiation  Gamma rays  highest energy on the EM spectrum  emitted by radioactive atoms  used to kill cancerous cells Radiation treatment using radioactive cobalt-60.