1. Conceptual Physical Science 5th Edition Chapter 11: LIGHT
© 2012 Pearson Education, Inc.

2. This lecture will help you understand:
Electromagnetic Spectrum
Transparent and Opaque Materials
Reflection
Refraction
Color
Dispersion
Polarization

3. Electromagnetic Nature of Light
electromagnetic waves created by vibrating electric charges having frequencies that fall within the range of sight
frequency of vibrating electrons equals the frequency of the light
travels nearly a million times faster than sound in air
light and all electromagnetic waves are transverse waves

4. Electromagnetic Spectrum
Electromagnetic wave
made up of vibrating electric and magnetic fields that regenerate each other by electromagnetic induction

5. Electromagnetic Spectrum
The Electromagnetic Spectrum

6. Electromagnetic Spectrum
CHECK YOUR NEIGHBOR
The electromagnetic spectrum spans waves ranging from lowest to highest frequencies. The smallest portion of the electromagnetic spectrum is that of
A. radio waves.
microwaves.
visible light.
gamma rays.
C. visible light.

7. Electromagnetic Spectrum
CHECK YOUR ANSWER
The electromagnetic spectrum spans waves ranging from lowest to highest frequencies. The smallest portion of the electromagnetic spectrum is that of
A. radio waves.
microwaves.
visible light.
gamma rays.
Explanation:
This can be inferred by a careful study of the spectrum and its regions in Figure 11.3.
C. visible light.

8. Electromagnetic Nature of Light
Order of increasing frequency of visible light:
red
violet—nearly twice the frequency of red
ultraviolet—cause of sunburns
X-rays
gamma rays

9. Electromagnetic Nature of Light
A situation to ponder…
A photographer wishes to photograph a lightning bolt by setting a camera so that it is triggered by the sound of thunder.
Put the correct answer here including the letter designation.

10. Is this a good idea or a poor idea?
A situation to ponder…
CHECK YOUR NEIGHBOR
Is this a good idea or a poor idea?
A. Good idea for nearby lightning strikes.
Good idea for all strikes.
Poor idea for nearby lightning strikes.
Poor idea for all strikes.
D. Poor idea for all strikes.

11. Is this a good idea or a poor idea?
A situation to ponder…
CHECK YOUR ANSWER
Is this a good idea or a poor idea?
A. Good idea for nearby lightning strikes.
Good idea for all strikes.
Poor idea for nearby lightning strikes.
Poor idea for all strikes.
Explanation:
Light travels about a million times faster than sound. By the time the sound of thunder arrives, the lightning bolt is long gone.
D. Poor idea for all strikes.

12. Transparent and Opaque Materials
colored glass is opaque to much of incident white light

13. Transparent and Opaque Materials
Light incident on:
dry surfaces bounces directly to your eye
wet surfaces bounces inside the transparent wet region, absorbing energy with each bounce, and reaches your eye darker than from a dry surface

14. Transparent and Opaque Materials
Light is transmitted similar to sound
light incident on matter forces some electrons in matter to vibrate

15. Transparent and Opaque Materials
How light penetrates a pane of glass
electrons in atoms of glass are forced into vibration
energy is momentarily absorbed and vibrates electrons in the glass
a vibrating electron either emits a photon or transfers the energy as heat
light slows due to time delay between absorption and reemission of photons

16. Transparent and Opaque Materials
Average speed of light through different materials
vacuum—c (300,000,000 m/s)
atmosphere—slightly less than c (but rounded off to c)
water—0.75 c
glass—0.67 c, depending on material
diamond—0.41 c

17. Strictly speaking, the photons of light incident on glass are
Transparent and Opaque Materials
CHECK YOUR NEIGHBOR
Strictly speaking, the photons of light incident on glass are
A. also the ones that travel through and exit the other side.
not the ones that travel through and exit the other side.
absorbed and transformed to thermal energy.
diffracted.
B. not the ones that travel through and exit the other side.

18. Strictly speaking, the photons of light incident on glass are
Transparent and Opaque Materials
CHECK YOUR ANSWER
Strictly speaking, the photons of light incident on glass are
A. also the ones that travel through and exit the other side.
not the ones that travel through and exit the other side.
absorbed and transformed to thermal energy.
diffracted.
Explanation:
Figure 11.6 illustrates this nicely. A photon that exits the glass is not the same photon that began the process of absorption and re-emission.
B. not the ones that travel through and exit the other side.

19. Reflection Reflection:
the returning of a wave to the medium through which it came when encountering a reflective surface
Law of reflection:
angle of incidence = angle of reflection

20. Reflection Virtual image
same size as object, formed behind a mirror, and located at the position where the extended reflected rays converge
as far behind the mirror as the object is in front of the mirror

21. Reflection Plane mirror
note, the only axis reversed in an image is the front-back axis

22. Reflection Curved mirrors form a different virtual image
convex mirror (that curves outward): virtual image is smaller and closer to the mirror than the object
concave mirror (that curves inward): virtual image is larger and farther away than the object

23. Reflection Diffuse reflection
light striking a rough or irregular surface reflects in many directions
an undesirable circumstance is the ghost image that occurs on a non-cable TV set when TV signals bounce off buildings and other obstructions

24. Diffuse Reflection Application
The open-mesh parabolic dish is a diffuse reflector for short-wavelength light.
It is also a polished reflector for long-wavelength radio waves.

25. Diffuse Reflection
Different road surfaces determine amount of diffuse reflection
Rough road surface—diffuse reflection of illumination from your car headlights lets you see road ahead at night
Wet road surface is smooth—more plane mirror than diffuse, so seeing road ahead is more difficult
Now you know!

26. When you stand 2 meters in front of a plane mirror, your image is
Reflection
CHECK YOUR NEIGHBOR
When you stand 2 meters in front of a plane mirror, your image is
A. 2 meters in back of the mirror.
4 meters from you.
Both A and B.
None of the above.
C. Both A and B.

27. When you stand 2 meters in front of a plane mirror, your image is
Reflection
CHECK YOUR ANSWER
When you stand 2 meters in front of a plane mirror, your image is
A. 2 meters in back of the mirror.
4 meters from you.
Both A and B.
None of the above.
C. Both A and B.

28. Refraction Refraction
bending of light when it passes from one medium to another
caused by change in speed of light

29. Refraction
Here we see light rays pass from air into water and from water into air
pathways are reversible for both reflection and refraction

30. Refracted light that bends toward the normal is light that has
Refraction
CHECK YOUR NEIGHBOR
Refracted light that bends toward the normal is light that has
A. slowed down.
sped up.
nearly been absorbed.
diffracted.
A. slowed down.

31. Refracted light that bends toward the normal is light that has
Refraction
CHECK YOUR ANSWER
Refracted light that bends toward the normal is light that has
A. slowed down.
sped up.
nearly been absorbed.
diffracted.
A. slowed down.

32. Refracted light that bends away from the normal is light that has
Refraction
CHECK YOUR NEIGHBOR
Refracted light that bends away from the normal is light that has
A. slowed down.
sped up.
nearly been absorbed.
diffracted.
B. sped up

33. Refracted light that bends away from the normal is light that has
Refraction
CHECK YOUR ANSWER
Refracted light that bends away from the normal is light that has
A. slowed down.
sped up.
nearly been absorbed.
diffracted.
Explanation:
This question is a consistency check with the question that asks about light bending toward the normal when slowing.
B. sped up.

34. Refraction Illusions caused by refraction
Objects submerged in water appear closer to the surface.

35. Refraction Illusions caused by refraction (continued)
Objects such as the Sun seen through air are displaced because of atmospheric refraction.

36. Refraction Illusions caused by refraction (continued)
Atmospheric refraction is the cause of mirages.

37. Refraction CHECK YOUR NEIGHBOR
Which of these would not exist if light didn’t slow in transparent materials?
A. Rainbows.
Mirages.
Magnifying glasses.
All wouldn’t be.
D. All wouldn’t be.

38. Refraction CHECK YOUR ANSWER
Which of these would not exist if light didn’t slow in transparent materials?
A. Rainbows.
Mirages.
Magnifying glasses.
All wouldn’t be.
D. All wouldn’t be.

39. Color
Color we see depends on frequency of light ranging from lowest (red) to highest (violet).
In between are colors of the rainbow.
Hues in seven colors: red, orange, yellow, green, blue, indigo, and violet.
Grouped together, they add to appear white.

40. Color Most objects don’t emit light, but reflect light.
Selective Reflection
Most objects don’t emit light, but reflect light.
A material may absorb some of the light and reflect the rest.
Selective Transmission
The color of a transparent object depends on the color of the light it transmits.

41. Color Mixed Color Lights
Three types of cone receptors in our eyes perceive color—each stimulated by only certain frequencies of light:
lower-frequency light stimulate cones sensitive to low frequencies (red)
Middle-frequency light stimulate cones sensitive to mid-frequencies (green)
High-frequency light stimulate cones sensitive to high frequencies (blue)
Stimulation of all three cones equally, we see white light

42. Color Additive primary colors (red, blue, green): red + blue = magenta
red + green = yellow
blue + green = cyan

43. Color Opposites of primary colors: opposite of green is magenta
opposite of red is cyan
opposite of blue is yellow
The addition of any color to its opposite color results in white.

44. Dispersion Dispersion
process of separation of light into colors arranged by frequency
Components of white light are dispersed in a prism (and also in a diffraction grating)

45. When white light passes through a prism, green light is bent more than
Dispersion
CHECK YOUR NEIGHBOR
When white light passes through a prism, green light is bent more than
A. blue light.
violet light.
red light.
None of the above.
C. red light.

46. When white light passes through a prism, green light is bent more than
Dispersion
CHECK YOUR ANSWER
When white light passes through a prism, green light is bent more than
A. blue light.
violet light.
red light.
None of the above
C. red light.

47. Dispersion
Rainbows
a colorful example of dispersion

48. Dispersion
Rainbow detail

49. Dispersion Rainbow facts
an observer is in a position to see only a single color from any one droplet of water
your rainbow is slightly different from the rainbow seen by others
your rainbow moves with you
disk within the bow is brighter because of overlapping of multiple refractions (which don’t occur outside the disk)

50. Dispersion Rainbow facts (continued)
secondary rainbow is fainter (due to two internal reflections and refracted light loss).
secondary bow is reversed in color (due to the extra internal reflection)

51. Compared with the primary rainbow, the secondary bow
Dispersion
CHECK YOUR NEIGHBOR
Compared with the primary rainbow, the secondary bow
A. is dimmer.
has colors reversed.
is caused by two internal reflections.
All of the above.
D. All of the above.

52. Compared with the primary rainbow, the secondary bow
Dispersion
CHECK YOUR ANSWER
Compared with the primary rainbow, the secondary bow
A. is dimmer.
has colors reversed.
is caused by two internal reflections.
All of the above.
D. All of the above.

53. Polarization Polarization
alignment of transverse electric vectors in electromagnetic waves
property of transverse waves
Left: E & M wave is polarized Right: rope vibrations are polarized
In both cases, wave is in the same plane as the plane of vibration.

54. Polarization Unpolarized light
vibrations producing light are in random directions

55. Polarization Polarized light
Unpolarized light divided into two internal beams polarized at right angles to each other. One beam is absorbed while the other beam is transmitted.

56. Polarization Polarized light (continued)
Use your knowledge of vectors and vector components to explain how light that can’t pass through a pair of Polaroids at right angles to each other will pass light when a third Polaroid is sandwiched between them!

57. Polarization occurs for waves that are
CHECK YOUR NEIGHBOR
Polarization occurs for waves that are
A. transverse.
longitudinal.
Both A and B.
Neither A nor B.
A. transverse.

58. Polarization occurs for waves that are
CHECK YOUR ANSWER
Polarization occurs for waves that are
A. transverse.
longitudinal.
Both A and B.
Neither A nor B.
A. transverse.