1. Ch. 18 - 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 Energy Carry 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. Electromagnetic Waves
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. corresponds to the amount of energy carried by the wave
B. Transverse Waves
Wave Anatomy
corresponds to the amount of energy carried by the wave
crests
wavelength
amplitude
nodes
troughs

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 compression wavelength rarefaction
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)
1 second
shorter wavelength  higher frequency  higher energy

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

12. v =  × f F. 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)

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

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

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

16. Ch. 17 – Waves II. Wave Behavior Doppler effect 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
Normal
Reflection
when a wave strikes an object and bounces off
incident beam
reflected beam

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.

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
Insert a movie clip

32. converted to nerve impulses in cochlea
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: ,000 Hz
ultrasonic waves
Insert fat lady singing
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
DECIBEL SCALE
120
110
100 80 70 40 18 10

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 source Moving source Supersonic source
waves combine to produce a shock wave called a sonic boom
same frequency in all directions
higher frequency
lower frequency

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

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

40. A. 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. B. Electromagnetic Spectrum
The full range of light

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 R O Y G. B I V
red
orange
yellow
green
blue
indigo
violet

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. Radiation treatment using radioactive cobalt-60.
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.

51. Ch. 19 - Light II. Light and Color (p.528-535) Light and Matter
Seeing Colors
Mixing Colors

52. A. Light and Matter Opaque absorbs or reflects all light Transparent
allows light to pass through completely
Translucent
allows some light to pass through

53. B. Seeing Colors White light contains all visible colors - ROY G. BIV
In white light, an object…
reflects the color you see
absorbs all other colors
REFLECTS
ALL COLORS
ABSORBS
ALL COLORS

54. Stimulates red & green cones
B. Seeing Colors
Stimulates red & green cones
The retina contains…
Rods - dim light, black & white
Cones - color
red - absorb red & yellow
green - absorb yellow & green
blue - absorb blue & violet
Stimulates all cones

55. Test for red-green color blindness.
B. Seeing Colors
Test for red-green color blindness.
Color Blindness
one or more sets of cones does not function properly

56. View Java Applet on primary light colors.
C. Mixing Colors
Primary light colors
red, green, blue
additive colors
combine to form white light
EX: computer RGBs
View Java Applet on primary light colors.

57. View Java Applet on filters.
C. Mixing Colors
Filter
transparent material that absorbs all light colors except the filter color
View Java Applet on filters.

58. C. Mixing Colors Pigment
colored material that absorbs and reflects different colors
Primary pigment colors
cyan, magenta, yellow
subtractive colors
combine to form black
EX: color ink cartridges

59. C. Mixing Colors Light Pigment
When mixing pigments, the color of the mixture is the color of light that both pigments reflect.

61. Negative Afterimage - One set of cones gets tired, and the remaining cones produce an image in the complimentary color.

62. III. Wave Properties of Light
Ch Light
III. Wave Properties of Light
(p )
Reflection
Refraction
Diffraction
Interference

63. 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

64. A. Reflection Reflection when a wave strikes an object and bounces off
Normal
Reflection
when a wave strikes an object and bounces off
incident beam
reflected beam

65. 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

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

67. B. Refraction
Example:
View explanation.

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

69. D. Interference Interference constructive  brighter light
destructive  dimmer light

70. E. Cool Applications! Fiber Optics Total Internal Reflection
when all light is reflected back into the denser medium

71. E. Cool Applications! The “Broken Pencil” refraction
View animation and explanation of the “Broken Pencil.”

72. E. Cool Applications!
Rainbows
refraction-reflection-refraction

73. E. Cool Applications! Diffraction Gratings
glass or plastic made up of many tiny parallel slits
may also be reflective
spectroscopes, reflective rainbow stickers, CD surfaces

74. E. Cool Applications! Thin Films - Bubbles & Oil Slicks
interference results from double reflection

75. E. Cool Applications! Blue Sky & Red Sunsets
Molecules in atmosphere scatter light rays.
NOON
less atmosphere
less scattering
blue sky, yellow sun
Shorter wavelengths (blue, violet) are scattered more easily.
SUNSET
more atmosphere
more scattering
orange-red sky & sun