1. Chapter 22—The Nature of Light
Material on the Final Exam

2. Section 1—What is Light? Objectives
How is light an electromagnetic wave?
Explain how you could calculate distances traveled by light using the speed of light
Explain why light from the sun is important

3. Light: An Electromagnetic Wave
Light travels as a wave
Light does not need matter to travel
Light is an electromagnetic wave
Electromagnetic waves are waves that consist of electric and magnetic fields that vibrate at right angles to each other

4. Electromagnetic Wave

5. Electric and Magnetic Fields
An electric field surrounds every charged object
A magnetic field surrounds every magnet

6. How EM Waves are Produced
Produced by the vibration of an electrically charged particle
Creates electric field
Field starts vibrating
Creates magnetic field
Carries energy

8. The speed of light Fastest thing known to science In a vacuum
300,000,000 m/s
300,000 km/s
Slows down in matter
Faster than sound

9. The speed of light
We can use the speed of light to find how far it travels
Formula
SI units for speed: m/s
SI units for distance: m
SI units for time: s
Speed = distance
time

10. Math Practice Math Practice You try!
The distance from Earth to the moon is 384,000 km. Calculate the time it takes for light to travel that distance.
You try!
The distance from the sun to Venus is 108,000,000 km. Calculate the time it takes for light to travel that distance.

11. Math Practice Math Practice You try!
It takes 2595 seconds (43 min) for light from the sun to reach Jupiter. How far away is Jupiter?
You try!
The alpha centauri system has two stars. If it takes 11470s for light to reach one star to the other, how far apart are they?

12. Light from the Sun Light is a major energy source for our planet
Plants use it to make food
Animals eat these plants
Fossil fuels store solar energy from the past

13. Section 1—What is Light? Objectives
How is light an electromagnetic wave?
Explain how you could calculate distances traveled by light using the speed of light
Explain why light from the sun is important

14. Chapter 22

15. 22-1 Study Guide Must have 3 colors Must draw and label and EM wave
Must describe the two waves that make up an EM wave
Must show the speed of light number
Must show the speed of light formula OR formula triangle
Must give 2 reasons why light from the sun is important

16. Section 2—The electromagnetic Spectrum
Objectives
Identify the two ways that EM waves differ from each other
Describe some uses for radio waves and microwaves
List examples of how infrared waves and visible light are important in your life
Explain how ultraviolet light, X rays, and gamma rays can be both harmful and helpful

17. Characteristics of EM waves
Light is only a teeny part of all EM waves
The electromagnetic spectrum is the entire range of EM waves
Divided by wavelength and frequency

19. Radio Waves Longest wavelengths (30+ cm) Lowest frequencies
Used for broadcasting radio signals
Modify frequency or amplitude (height) of wave
AM and FM radio

20. Radio Waves FM versus AM Radio AM has longer wavelengths
AM bounce off atmosphere
FM less affected by electrical “noise”
Why FM sounds better

21. Radio waves and Television
TV signals carried by radio waves
Shorter wavelengths than radio
Higher frequencies than radio
Change frequency and amplitude
Sent to satellites to amplify signal

22. Microwaves
Shorter wavelengths (1mm-30cm) and higher frequencies than radio
Microwave ovens, Radar and communication

23. Radar From microwaves Radio detection and ranging
Finds speed and location of object
Sends waves that bounce off items

24. Infrared Waves
Shorter wavelengths (700 nm to 1mm) and higher frequencies than microwaves
“Warm” feeling on sunny day
Heat
Invisible for us, but can be detected--thermogram

26. Visible Spectrum
Narrow range of wavelengths and frequencies that humans can see
White light is the combination of all colors of light

27. Ultraviolet Light
Shorter wavelengths (60-400nm) and higher frequencies than visible light
Both good and bad for your body

28. Ultraviolet Light Good Effects Bad Effects Kill bacteria on food
Sterilize surgical tools
Helps body make vitamin D
Helps with calcium absorption
Bad Effects
Sunburn
Skin cancer, wrinkles, eye damage
Protected by ozone, clothing and sunscreen

29. X rays and Gamma Rays X rays Gamma rays .001nm-60nm wavelength
Medical field
Kill cells
Lead aprons
Airport security
Gamma rays
Shortest wavelengths (<0.1nm) and highest frequency
Penetrate almost all materials
Treat cancer
Kill cells
Kill bacteria on food

30. Section 2—The electromagnetic Spectrum
Objectives
How do EM waves differ from each other?
Describe some uses for radio waves and microwaves
List examples of how infrared waves and visible light are important in your life
Explain how ultraviolet light, X rays, and gamma rays can be both harmful and helpful

31. 22-2 Study Guide Must have 3 colors
Must write the EM waves in order from long λ to short λ
Must show wavelength, frequency, and energy trend from left to right
Must list the two ways that EM waves differ from each other
Must include one use of each wave
Give one harm for UV

32. Section 3—Interactions of Light Waves
Objectives
Describe how reflection allows you to see things
Describe absorption and scattering
Explain how refraction can create optical illusions
Explain how refraction can separate white light into colors
Compare constructive and destructive interference of light

33. Reflection Reflection is when light waves bounce off an object
EX: mirror
The Law of Reflection states that the angle of incidence is equal to the angle of reflection
The angle it comes in is the same angle it goes out

35. Types of Reflection
Regular Reflection is when all light beams are reflected at the same angle
Smooth surfaces
Diffuse Reflection is when light beams reflect at many different angles
Not smooth

36. Light Source or Reflection?
Luminous objects produce visible light
Light source
Illuminated objects are visible objects that are not a light source
Due to the light around it (reflection

37. Absorption and Scattering
Absorption is the transfer of energy carried by light waves to particles of matter
Air absorbs some energy
Why a flashlight dims
Farther the light source, the more light that gets absorbed

38. Absorption and Scattering
Scattering is an interaction of light with matter that causes light to change direction
All directions
See objects outside beam
WHY THE SKY IS BLUE!

39. Refraction
Refraction is the bending of a wave as it passes at an angle from one substance to another

40. Refraction Why does refraction happen
Light travels at different speeds when it goes through different things

41. Refraction When light switches materials, it speeds up or slows down
This changes the angle

42. Diffraction
Diffraction is the bending of waves around barriers or through openings
Depends on wave size
Depends on barrier size

43. Diffraction and Wavelength
Small wavelength for light!
Does not bend much unless opening is even smaller
Why light does not bend around corners

44. Interference
Interference is a wave interaction that happens when two or waves overlap
Can brighten: constructive
Can dim: destructive

45. Constructive v. destructive interference

46. Section 3—Interactions of Light Waves
Objectives
Describe how reflection allows you to see things
What is the difference between absorption and scattering
How can refraction separate white light into colors
What is the difference between constructive and destructive interference?

47. 22-3 Study Guide Must have 3 colors
Be able to Label and draw examples for
Regular Reflection
Diffuse Reflection
Absorption
Scattering
Refraction
Diffraction

48. Section 4—Light and Color
Objectives
Name and describe the three ways light interacts with matter
Explain how the color of an object is determined
Describe color addition and color subtraction

49. Light and Matter When light strikes objects, it can be Reflected
Absorbed
Transmitted

50. Reflection, Absorption,Transmission
Reflection is when light bounces off an object
Absorption is when light energy is transferred to matter
Transmission is the passing of light through matter

51. Types of Matter
Transparent matter is matter through which visible light is easily transmitted
Ex: glass, plastic wrap

52. Types of Matter
Translucent matter transmits light but also scatters it
Ex: frosted glass, wax paper

53. Types of Matter
Opaque matter is matter that does not transmit any light
Ex: Aluminum foil, a book, wood

54. Colors of Objects
Color is about the reflection of light off materials that hits your eyes

55. Colors of objects Translucent objects Opaque objects
The colors you see are the colors that are transmitted
Opaque objects
The colors you see are the colors that are reflected
White = ALL colors reflected
Black = ALL colors absorbed

56. Mixing colors of light Only need 3 colors to make white light
Red
Green
Blue
Called primary colors of light

57. Color addition Combining colors of light is called color addition
Mixing two primary light colors makes secondary light colors

58. Colored Television
Television has color because each “dot” has a group of red, green, and blue dots
Different combinations give us color

59. Mixing colors of pigment
A pigment is a material that gives a substance its color by absorbing some color of light and reflecting others
Primary pigments
Magenta
Yellow
Cyan

60. Color subtraction
Mixing pigments results in more colors being absorbed or taken away—color subtraction

61. 22-4 Study Guide Must have 3 colors
Pick SEVEN facts from this section to include
You can do vocab, pictures, examples, etc.

62. Section 4—Light and Color
Objectives
Name and describe the three ways light interacts with matter
Explain how the color of an object is determined
Describe color addition and color subtraction