2. Chapter: Sound and Light
Table of Contents
Chapter: Sound and Light
Section 1: Sound
Section 2: Reflection and Refraction
of Light
Section 3: Mirrors, Lenses, and the Eye
Section 4: Light and Color

3. Sound 1 When an object vibrates, it creates sound waves.
Sound waves are compressional waves.
The compression moves away as these molecules collide with other molecules in air.
A rarefaction is formed where the molecules are farther apart.
This series of compressions and rarefactions is the sound wave that you hear.

4. Sound 1 The material in which a sound wave moves is called a medium.
Sound waves travel in solids, liquids, and other gases as a vibrating object transfers energy to the particles in the material.

5. Sound 1
Sound
The speed of a sound wave in a medium depends on the type of substance and whether it is a solid, liquid, or gas.
Sound travels slowest in gases and fastest in solids.

6. Amplitude and Energy of Sound Waves1
Amplitude and Energy of Sound Waves
The amount of energy a wave carries corresponds to its amplitude.
More energy is transferred to the medium when the particles of the medium are forced closer together in the compressions and spread farther apart in the rarefactions.

7. Amplitude and Energy of Sound Waves1
Amplitude and Energy of Sound Waves

8. Intensity and Loudness
Sound 1
Intensity and Loudness
The amount of energy transferred by a sound wave through a certain area each second is the intensity of the sound wave.
Loudness is the human perception of sound intensity.

9. Intensity and Loudness
Sound 1
Intensity and Loudness
Each unit on the scale for sound intensity is called a decibel.

10. Sound 1
Pitch and Frequency
Pitch is the human perception of the frequency of sound waves.
Frequency is a measure of how many wavelengths pass a particular point each second.

11. Pitch and Frequency 1 Frequency is measured in hertz (Hz).
Sound 1
Pitch and Frequency
Frequency is measured in hertz (Hz).
A healthy human ear can hear sound waves with frequencies from about 20 Hz to 20,000 Hz.
Sound frequencies above 20,000 Hz are called ultrasonic waves.
Infrasonic, or subsonic, waves have frequencies below 20 Hz.

12. Sound 1
Doppler Effect
The change in pitch or frequency due to the relative motion of a wave source is called the Doppler effect.

13. A Moving Source of Sound1
A Moving Source of Sound

14. Sound 1
A Moving Listener
You also can hear the Doppler effect when you are moving past a sound source that is standing still.
The Doppler effect happens any time the source of a sound is changing position relative to the listener.

15. Sound 1
Using Sound
Echolocation is the process of locating objects by emitting sounds and detecting the sound waves that reflect back.
Sonar is a system that uses the reflection of underwater sound waves to detect objects.
Reflected ultrasonic waves are used to examine different body parts.

16. Section Check 1
Question 1
Sound frequencies above 20,000 Hz are called __________ waves.
A. infrasonic
B. infrared
C. subsonic
D. ultrasonic

17. Section Check 1
Answer
The answer is D. Subsonic and infrasonic are waves with frequencies below 20 Hz.

18. Question 2 Answer 1 Describe the Doppler effect.
Section Check 1
Question 2
Describe the Doppler effect.
Answer
The Doppler effect is the change in pitch due to a moving wave source.

19. Section Check 1
Question 3
In which of the following environments would sound waves not travel?
A. at altitudes of 10,000 – 15,000 m
B. in solid aluminum
C. on the Moon
D. under water

20. Section Check 1
Answer
The answer is C. Sound waves require a medium through which to travel. So, sound waves cannot travel through empty space.

21. The Interaction of Light and Matter
Reflection and Refraction of Light 2
The Interaction of Light and Matter
Absorption, Transmission, and Reflection
The opaque material in this candleholder only absorbs and reflects light—no light passes through it.

22. Absorption, Transmission, and Reflection
Reflection and Refraction of Light 2
Absorption, Transmission, and Reflection
Materials that allow some light to pass through them, like the material of this
candleholder are described as translucent.

23. Absorption, Transmission, and Reflection
Reflection and Refraction of Light 2
Absorption, Transmission, and Reflection
Transparent materials, such as this candleholder transmit almost all the light
striking them, so you can see objects clearly through them.

24. Regular and Diffuse Reflection
Reflection and Refraction of Light 2
Reflection of Light
Regular and Diffuse Reflection
A smooth, even surface such as a pane of glass produces a sharp image by reflecting parallel light waves in only one direction.
Reflection of light waves from a smooth surface is regular reflection.
To cause a regular reflection, the roughness of a surface must be less than the wavelengths it reflects.

25. Regular and Diffuse Reflection
Reflection and Refraction of Light 2
Regular and Diffuse Reflection
Reflection of light from a rough surface is diffuse reflection.
Diffuse reflection is a type of scattering that occurs when light waves traveling in one direction are made to travel in many different directions.

26. Reflection and Refraction of Light2
Refraction of Light
Refraction is caused by a change in the speed of a wave when it passes from one material to another.

27. Reflection and Refraction of Light2
Refraction of Light
Index of refraction is the ratio of the speed of light in a vacuum to the speed of light in the material.
The index of refraction indicates how much the speed of light is reduced in the material compared to its speed in empty space.
The larger the index of refraction, the more light is slowed down in the material.

28. Reflection and Refraction of Light2
Refraction of Light
White light, such as sunlight, is made up of light waves with range of wavelengths.
Prism refracts the light twice—once when it enters the prism and again when it leaves the prism.

29. Reflection and Refraction of Light2
Refraction of Light
The longer wavelengths of light are slowed less and are bent the least.
As a result, the different colors are separated when they emerge from the prism.

30. Reflection and Refraction of Light2
Mirages
Mirages result when the air at ground level is much warmer or cooler than the air above.

31. Reflection and Refraction of Light2
Mirages
The density of air increases as air cools and light waves move slower in cooler air than in warmer air.
Light waves are refracted as they pass through air layers with different temperatures.

32. Question 1 Answer 2 What happens to light waves that strike an object?
Section Check 2
Question 1
What happens to light waves that strike an object?
Answer
Light waves that strike objects can be absorbed, reflected, or transmitted.

33. Section Check 2
Question 2
What is the difference between refraction and reflection?
Answer
Refraction occurs if a light wave changes speed in moving from one material to another. Reflection occurs when light waves are returned or thrown back from a surface.

34. Section Check 2
Question 3
__________ material only absorbs and reflects light; no light passes through.
A. Transparent
B. Translucent
C. Opaque
D. Mirage

35. Section Check 2
Answer
The answer is C. Transparent and translucent materials both allow some light to pass through.

36. Light Rays Mirrors Plane Mirrors 3
Mirrors, Lenses, and the Eye 3
Light Rays
Mirrors
A mirror is any surface that produces a regular reflection.
Plane Mirrors
A flat smooth mirror is a plane mirror.

37. Plane Mirrors 3 Light rays from a light source strike you.
Mirrors, Lenses, and the Eye 3
Plane Mirrors
Light rays from a light source strike you.
Every point that is struck by the light rays reflects these rays so they travel outward in all directions.
Light rays are reflected from the mirror back to your eyes.

38. Virtual and Real Images
Mirrors, Lenses, and the Eye 3
Virtual and Real Images
Plane mirrors always form virtual images.
If light rays from an object pass through the location of the image, the image is called the real image.
If the surface of a mirror is curved inward, it is called a concave mirror.

39. Virtual and Real Images
Mirrors, Lenses, and the Eye 3
Virtual and Real Images
The image formed by a concave mirror depends on the location of the object relative to the focal point.

40. Virtual and Real Images
Mirrors, Lenses, and the Eye 3
Virtual and Real Images
An object between one and two focal lengths from a concave mirror is real, inverted, and larger than the object.
An object closer than one focal length from a concave mirror produces a virtual image that is upright and larger than the object.

41. Mirrors, Lenses, and the Eye3
Convex Mirrors
A mirror that curves outward like the back of a spoon is called a convex mirror.
so a convex mirror forms only a virtual image.
Reflected rays diverge and never meet,
The image also is upright and smaller than the actual object is.

42. Mirrors, Lenses, and the Eye3
Lenses
A lens is a transparent object with at least one curved surface that causes light rays to refract.
Convex Lenses
A convex lens is thicker in the middle than at the edges.

43. Mirrors, Lenses, and the Eye3
Convex Lenses
Light rays are refracted toward the center of the lens.
All light rays are refracted so they pass through a single point, which is the focal point of the lens.

44. Convex Lenses 3 Lenses with flatter sides have longer focal lengths.
Mirrors, Lenses, and the Eye 3
Convex Lenses
Lenses with flatter sides have longer focal lengths.

45. Mirrors, Lenses, and the Eye3
Concave Lenses
A concave lens is thinner in the middle and thicker at the edges.
Light rays that pass through a concave lens bend away from the optical axis.

46. Mirrors, Lenses, and the Eye3
The Human Eye
Light enters your eye through a transparent covering on your eyeball called the cornea.
The cornea causes light rays to bend so that they converge.
Light then passes through the pupil.

47. The Human Eye 3 Behind the pupil is a flexible convex lens.
Mirrors, Lenses, and the Eye 3
The Human Eye
Behind the pupil is a flexible convex lens.
containing light sensitive cells that convert an image into electrical signals.
The retina is the inner lining of your eye,

48. Brightness and Intensity
Mirrors, Lenses, and the Eye 3
Brightness and Intensity
The human eye can adjust to the brightness of the light that strikes it.
Light intensity is the amount of light energy that strikes a certain area each second.
Brightness is the human perception of light intensity.
Eyes respond to bright light by decreasing the size of your pupil.

49. Correcting Vision Problems
Mirrors, Lenses, and the Eye 3
Correcting Vision Problems
If you can see distant objects clearly but can’t bring nearby objects into focus, then you are farsighted.

50. Correcting Vision Problems
Mirrors, Lenses, and the Eye 3
Correcting Vision Problems
The eyeball might be too short or the lens isn’t curved enough to form a sharp image of nearby objects on the retina.

51. Mirrors, Lenses, and the Eye3
Nearsightedness
Eyes cannot form a sharp image on the retina of an object that is far away.
The image is formed in front of the retina.

52. Question 1 3 A __________ mirror curves inward. A. concave B. convex
Section Check 3
Question 1
A __________ mirror curves inward.
A. concave
B. convex
C. obtuse
D. plane

53. Section Check 3
Answer
The answer is A. A concave mirror curves inward and forms a real image. A convex mirror curves outward and forms a virtual image.

54. Section Check 3
Question 2
What type of lens refracts light rays away from the optical axis?
Answer
Concave lenses are thicker at the edges and refract light rays away from the optical axis.

55. Section Check 3
Question 3
In nearsightedness, the image forms _______ the retina and a _______ lens can be used to correct it.
A. behind, concave
B. behind, convex
C. in front of, concave
D. in front of, convex

56. Section Check 3
Answer
The answer is C. The image forms in front of the retina and a concave lens corrects it.

57. Light and Color 4
Why Objects Have Color
White light is a blend of all colors of visible light.
Black is the absence of visible light.

58. Light and Color 4
Colored Filters
A filter is a transparent material that transmits one or more colors of light but absorbs all others.
The color of a filter is the color of the light that it transmits.

59. Light and Color 4
Seeing Color
The retina is made up of two types of cells that absorb light.
A cone enables you to distinguish colors and detailed shapes of objects.

60. Cones and Rods 4 Your eyes have three types of cones.
Light and Color 4
Cones and Rods
Your eyes have three types of cones.
Red cones respond to mostly red and yellow light.
Green cones respond to mostly yellow and green.

61. Cones and Rods 4 Blue cones respond to mostly blue and violet light.
Light and Color 4
Cones and Rods
Blue cones respond to mostly blue and violet light.
A rod is sensitive to dim light and enables you to see at night.
Rod cells do not enable you to see colors.

62. Light and Color 4
Color Blindness
If cone cells do not function properly, you might not be able to distinguish certain colors.
This condition is called color blindness.
The most common form of color blindness makes it difficult to distinguish between red and green.

63. Light and Color 4
Mixing Colors
A pigment is a colored material that is used to change the color of other substances.
Red, green, and blue are the primary colors of light.
Mixing the primary colors in different proportions can produce the colors you see.

64. Light and Color 4
Mixing Pigments
You can make any pigment color by mixing different amounts of the three primary pigments—magenta, cyan, and yellow.
Pigments both absorb and reflect a range of colors.

65. Light and Color 4
Mixing Pigments
The area where the colors overlap appears to be black because the three blended primary pigments absorb all the primary colors of light.

66. Section Check 4
Question 1
An object’s color depends on the __________ it reflects.
Answer
An object’s color depends on the wavelengths of light it reflects. If an object absorbs all wavelengths of visible light except green, the object appears green.

67. Section Check 4
Question 2
What are the two types of light-detecting cells in the eye?
Answer
The two types of light-detecting cells that make up the retina are the rods and cones.

68. Section Check 4
Question 3
What is the appearance of the three primary colors of pigment when they are mixed?
A. black
B. brown
C. gray
D. white

69. Section Check 4
Answer
The answer is A. The three primary colors of pigment are magenta, cyan and yellow, and appear black when they are mixed.

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