1. Speed of light The speed of light is 3.0 x 108 m/s in a vacuum
3.0 x 108 m/s = m/s
But what does that even mean?

2. Speed of Light A passenger jet travels at about 900 km/h (250 m/s)
It would take a jet 45 hours to fly around the world at the equator
(and that’s not including time to refuel)

3. Speed of Light
If we could move at the speed of light, we could circle the earth 7.5 times in one second

4. Speed of light
Okay, but I say the speed of light is 3.0 x 108 m/s in a vacuum
Why did I say “in a vacuum”? ?

5. Imagine This...
Think, Pair, Share

6. Refraction
The bending or change in direction of light when it travels from one medium to another.

7. angle of incidence incident ray medium A medium B refracted angle of
refraction

8. The Speed of Light
It’s 3.0 x 108 m/s
... isn’t it?

9. Less friction
(less dense)
More friction
(more dense)

10. Less friction
(less dense)
This wheel slows down, but the others continue to move at the same speed
More friction
(more dense)

11. More friction
(more dense)
Less friction
(less dense)

12. More friction
(more dense)
This wheel speeds up, but the others continue to move at the same speed
Less friction
(less dense)

13. Both front wheels slows down.
Less friction
(less dense)
More friction
(more dense)
Both front wheels slows down.

14. Rules of Refraction
The incident ray, refracted ray, and the normal are all on the same plane. The incident ray and the refracted ray are on opposite sides of the line that separates the media.
The light bends towards the normal when the speed of the light in the second medium is less than the speed of light in the first medium.

15. Medium A
Medium B
Which medium:
Is less dense?
Has a higher index of refraction?
Is the light traveling slower?

17. 1 2
More Dense
Larger Index

18. 3
More Dense
Larger Index 4

19. 3
Same Density
Same Index 1

20. The Index of Refraction (n)
The ratio of the speed of light in a vacuum (c) to the speed of light in a medium (v)

21. Example #1
How fast does light travel through water? (The index of refraction of water is 1.33)
c = 3.00 x 108 m/s

22. Example #2
If the speed of light in a medium is x 108 m/s, which solid medium is light traveling through?

23. Lateral Displacement
Air
Air
Water
Lateral
Displacement

24. Think about it
If you place two pieces of glass beside each other and shone a light through them, which way would the light bend?
Towards the normal
Away from the normal
It would not bend
It depends on the index of refraction

25. Think about it
If you place two pieces of glass (with the same index of refraction) beside each other and shone a light through them, which way would the light bend?
Towards the normal
Away from the normal
It would not bend

27. Partial Reflection and Refraction Refraction is often accompanied by reflection. Some light is reflected off of the surface and the rest is refracted. We often observe this in water, windows, and sunglasses.

28. Total Internal Reflection
Critical Angle
Air
Water
Total internal reflection

29. Total Internal Reflection
Critical angle: The angle of incidence that results in an angle of refraction of 90º.
Total Internal Reflection: occurs when the angle of incidence is equal or greater than the critical angle.

30. Total Internal Reflection
Total internal reflections occurs when two conditions are met:
Light is travelling more slowly in the first medium than in the second
The angle of incidence is large enough that no refraction occurs

31. Critical Angle
48.8º
70º
25º

32. Fibre Optics

33. Converging Lens

34. Diverging Lens

35. Converging Lens O F
Focus F’
Optical Centre
focal length

36. Converging Lens incident ray emergent ray O F’ F focal length Focus

37. Simplifying the Path

38. Diverging Lens
Optical Centre O F F’
Focus
Focus

39. Converging Lens emergent ray incident ray O F F' focal length Focus

40. Aberration
A distortion of the image

41. Spherical Aberration
Irregularities in an image in a curved mirror or lens that result when rays to not go through the focus
This is more noticeable as the lens gets thicker

42. Chromatic Aberration The dispersion of light through a lens
Dispersion is the process of separating colours by refraction

43. Overcoming Aberration

44. Converging Lens O 2F F F 2F
1. A ray parallel to the principle axis will be refracted through the (right) focus (F).
2. A ray through the (left) focus (F) is refracted parallel to the principle axis.
3. A ray through the optical centre (O) continues straight through without being refracted

45. Simplifying the Path

46. O 2F F F 2F
1. A ray parallel to the principle axis refracts as if it had come from the (left) focus (F).
2. A ray aimed at the (right) focus (F) is refracted parallel to the principle axis.
3. A ray through the optical centre (O) continues straight through without being refracted

47. Converging Lens Diverging Lens
1. A ray parallel to the principle axis will be refracted through the (right) focus (F).
2. A ray through the (left) focus (F) is refracted parallel to the principle axis.
3. A ray through the optical centre (O) continues straight through without being refracted
Diverging Lens
1. A ray parallel to the principle axis refracts as if it had come from the (left) focus (F).
2. A ray aimed at the (right) focus (F) is refracted parallel to the principle axis.
3. A ray through the optical centre (O) continues straight through without being refracted

48. Thin Lens Equation f: Focal length. Positive for converging lenses.
f: Focal length. Positive for converging lenses.
di: Image distance. Positive for real images, negative for virtual images
do: Object distance. Always positive.

49. Magnification Equation
m: Magnification.
hi: Image height. Positive for upright images, negative for inverted images
ho: Object height. Always positive.
di: Image distance. Positive for real images, negative for virtual images
do: Object distance. Always positive.

50. Practice Problem 1
A converging lens has a focal length of 12 cm. An object with a height of 4.0 cm is placed 18 cm in front of the lens.
Calculate the image distance
Calculate the image height
State the 4 image characteristics

51. Practice Problem 2
A converging lens has a focal length of 16 cm. A person who is 2.0 cm tall is standing 8 cm in front of the mirror.
Calculate the image distance
Calculate the image height
State the 4 image characteristics

52. Mirror Equation Practice
pg 500 #1 - 4

53. Characteristics of Images formed in a Converging Lens
Location of Object
Size
Attitude
Location
Type
Beyond 2F'
At 2F'
Between 2F' and F'
At F'
Inside F'
Between 2F and F
Smaller
Inverted
Real
Same size
Inverted
At 2F
Real
Larger
Inverted
Beyond 2F
Real
No clear image
Same side as the object
Larger
Upright
Virtual

54. Characteristics of Images formed in a Converging Lens
Location of Object
Size
Attitude
Location
Type
Beyond 2F'
At 2F'
Between 2F' and F'
At F'
Inside F'
Between 2F and F
Smaller
Inverted
Real
Same size
Inverted
At 2F
Real
Larger
Inverted
Beyond 2F
Real
No clear image
Same side as the object
Larger
Upright
Virtual