1. THE NATURE OF LIGHT

2. LET’S REVIEW What is a wave?
A disturbance that transmits energy through matter or space.
What do waves carry?
Energy
What is a medium?
Substance wave travels through
What kind of wave NEEDS a medium?
Mechanical wave

3. MORE REVIEW What kind of wave DOES NOT NEED a medium?
Electromagnetic wave
What wave’s particles vibrate up and down perpendicular to the direction the wave is traveling?
Transverse
What wave’s particles vibrate back and forth?
Longitudinal

4. EVEN MORE REVIEW
What are the highest and lowest parts of a transverse wave?
Crest and trough
What are the “close together” and “far apart” parts of a longitudinal wave?
Compression and rarefaction
Transverse + longitudinal =
Surface wave

5. CAN’T GET ENOUGH REVIEW
Explain amplitude
Height of wave = energy of wave
Tall amp = high energy short amp = low energy
Explain wavelength
Dist between crest/crest, trough/trough, compression/compression, rarefaction/rarefaction
Compare wavelength, frequency, and energy
Long λ = low frequency = low energy
Short λ = high frequency = high energy

6. ALMOST DONE WITH REVIEW
What is reflection?
Waves bounce back off barrier
What is refraction?
Waves bend at angle when changing media
What is diffraction?
Waves bend around barriers/go through openings
What is interference?
2+ waves overlap and share the same space
Contrast constructive interference and destructive interference.
CI = crest over crest DI = crest over trough

7. IN YOUR OPINION, WHAT IS LIGHT?

8. WHAT IS LIGHT? LIGHT: is a type of energy that travels as a wave.
Does NOT require a medium
Also known as an ELECTROMAGNETIC WAVE
An electromagnetic wave is a wave that can travel through space or matter and consists of changing electric and magnetic fields.
A field is the place around an object that exerts a force without touching.

9. ELECTROMAGNETIC WAVE

10. WHAT IS DIFFERENT ABOUT THESE TWO WAVES?

11. LIGHT CONTINUED ALL electromagnetic waves are transverse waves.
Electric fields vibrate and make a magnetic field
The emission of energy in the form of EM waves is radiation

12. MORE LIGHT
Light is produced when an electron loses the energy it gained when it jumped levels.
A photon is a tiny “packet” of energy

13. HOW FAST IS LIGHT?

14. IT’S THE FASTEST THING IN THE UNIVERSE!!!!!
The speed of light is
300,000,000 m/s or
3.0 x 108 m/s

15. LIGHT CAN TRAVEL AROUND THE EARTH 7.5 TIMES IN 1 SECOND!!!!!
HOW FAST IS THAT REALLY!?!
LIGHT CAN TRAVEL AROUND THE EARTH 7.5 TIMES IN 1 SECOND!!!!!

16. THE ELECTROMAGNETIC SPECTRUMor
EMS

17. EMS Not all light can be seen There are many types of EM waves
All EM waves travel at the same speed
Speed = wavelength x frequency
Same speed = different wavelength x different frequency
Electromagnetic spectrum is the entire range of EM waves

18. EMS consists of seven categories of waves.
RADIO WAVES MICROWAVES INFRARED VISIBLE LIGHT ULTRAVIOLET X-RAYS GAMMA RAYS

19. CAN YOU LABEL THE DIFFERENT WAVES ON THE PICTURES?

20. Long to short wavelength
EMS
EMS is arranged from:
Long to short wavelength or
Low to high frequency

21. CATEGORIES OF ELECTROMAGNETIC WAVES
WHAT CAN YOU TELL ME ABOUT THIS WAVE?
DECREASING WAVELENGTH AND INCREASING FREQUENCY R M I V U X G

22. CATEGORIES OF ELECTROMAGNETIC WAVES
Longest λ and lowest frequency
Low energy waves
Used to broadcast radio signals
Can not be heard, converted to sound
AM = amplitude modulation
FM = frequency modulation
Radio
waves
Micro-waves
Infrared
Visible Light
Ultra-violet
X-rays
Gamma rays

23. AM vs. FM
Travels longer distance carry more information

24. Radio Waves
RETURN

25. CATEGORIES OF ELECTROMAGNETIC WAVES
Shorter λ and higher f than radio waves
Carry more energy
Ex. Televisions, cell phones, microwave
ovens
Radar(radio detection and ranging) =
used for speed and location of
vehicles
Radio
waves
Micro-waves
Infrared
Visible Light
Ultra-violet
X-rays
Gamma rays

26. How does a microwave work?

27. Microwaves
RETURN

28. CATEGORIES OF ELECTROMAGNETIC WAVES
Also known as IR
Shorter λ and higher f than microwaves
Carries more energy than radio and microwaves
Feel warmth because of infrared
Ex. Body heat, stars, planets, trees
Warmer objects give off more infrared radiation
Radio
waves
Micro-waves
Infrared
Visible Light
Ultra-violet
X-rays
Gamma rays

29. Infra Red
RETURN

30. CATEGORIES OF ELECTROMAGNETIC WAVES
Narrow range of λs and frequencies
ONLY light humans can see
Different λ have different colors
Longest λ is red = low energy = low frequency
Shortest λ is violet = high energy = high frequency
Colors of light = ROY G BIV
Radio
waves
Micro-waves
Infrared
Visible Light
Ultra-violet
X-rays
Gamma rays

31. Visible Light The Visible Spectrum Color Red 610-750 4.9-4.0 Orange
Wavelength (nm)
Frequency (x 1014 Hz)
Red
Orange
Yellow
Green
Blue
Violet

32. Visible Light
RETURN

33. CATEGORIES OF ELECTROMAGNETIC WAVES
Also known as UV
Produced by the sun
Carry more energy than visible light
Positive: kills bacteria, vitamin D,
Negative: sunburn, skin cancer
use sunscreen with a high SPF(Sun Protection Factor)
Radio
waves
Micro-waves
Infrared
Visible Light
Ultra-violet
X-rays
Gamma rays

34. Ultraviolet light

35. CATEGORIES OF ELECTROMAGNETIC WAVES
Some of the shortest wavelengths and highest frequencies
Easily penetrates materials
Too much exposure can kill cells
Radio
waves
Micro-waves
Infrared
Visible Light
Ultra-violet
X-rays
Gamma rays

36. How do X-rays work?

37. X - Rays
RETURN

38. CATEGORIES OF ELECTROMAGNETIC WAVES
Carry the largest amount of energy
Penetrates material very easily
Exposed to gamma rays everyday but are not harmful
Used to treat cancer, but some good cells can be killed
Radio
waves
Micro-waves
Infrared
Visible Light
Ultra-violet
X-rays
Gamma rays

39. Gamma Rays
RETURN

40. Light Wave Interactions

41. Light waves bounce off an object
Light Reflection
Light waves bounce off an object
Allows for you to see objects that don’t produce light

42. Law of Reflection The angle of incidence = angle of reflection
Incidence = falling of light beam on surface

43. Why can we see ourselves in a mirror but not in a wall?

44. Regular/Specular Reflection
Types of Reflection
Regular/Specular Reflection
Diffuse Reflection

45. Absorption Scattering
More interactions
Absorption
Scattering
Transfer of energy carried by light waves to particles of matter.
Release of light energy by particles of matter that have absorbed energy

46. Absorption and Scattering

47. Light Refraction
Bending of a wave at an angle as it passes from one medium to another.
If light passes into a medium where the
speed of light is slower, the light bends away from the boundary between the media.
If light passes into a medium where the speed of light is faster, the light bends toward the boundary.

48. Refraction and Color Separation
White light = combined colors of visible light
Amount of light refracted depends on λ
Short λ = ↑ bending Long λ = ↓ bending

49. SITE FOR WHITE LIGHT COLORS
SITE FOR WHITE LIGHT COLORS

50. Light Diffraction Bending of waves around barriers or through openings
Light diffraction is difficult to see
Can not diffract much around large objects
Causes shadow edges to be blurry

51. Diffraction and Interference
Diffraction and Interference
Constructive interference = bright light
Deconstructive interference = dark light

54. Light and Color

55. Light interacts with matter by:
Reflection Absorption Transmission

56. How is light interacting below?
REFLECTION
TRANSMISSION
ABSORPTION

57. Passing of light through matter
Transmission:
Passing of light through matter

58. Easy to transmit light or not?

59. TRANSPARENT Light transmitted easily Can see object’s CLEARLY
Ex. Air, glass, water, clear wrap

60. TRANSLUCENT Light transmits but also some scatters Hard to see objects
Ex. Frosted glass, wax paper

61. OPAGUE Light not transmitted at all Cannot see objects at all
Ex. Metal, wood, aluminum foil

62. Seeing Colors
Occurs because of reflection, transmission, or absorption

63. What about opaque colors?
White light shines on strawberry
Red light is reflected
All other colors absorbed

64. What about black and white?
ALL colors are reflected to get color white
ALL colors are absorbed to get color black

65. Transparent and Translucent Objects
Green transmitted through material
All other colors absorbed
If clear, all colors transmitted

66. Mixing Colors of Light
White light = all light combined or blue + green+ red(primary colors)
Cyan
Green
Blue
Yellow
Magenta
Red
Secondary colors = 2 primary colors added together
(blue + red = magenta) (red + green = yellow)
(blue + green = cyan)

67. What color do you get when you mix blue, green, and red paint?

68. Mixing Colors of Pigment
Can not mix primary colors to get white
Paint contains pigments
pigment: gives substance color by absorbing some light colors and reflecting others