1. L13 Putting All Refraction Together Answers to Student Notes Less to Dense and Back Again, Lateral Displacement Big Fish Bent Pencils Total Internal Reflection (TIR) Fish Eye Views
Stars indicate activities are available to backup theory.

2. Optically Less Dense (air)into More Dense (glass)
Light Travelling From
Optically Less Dense (air)into More Dense (glass)
When light travels from air to glass it bends towards the normal.

3. Optically Less Dense (air)into More Dense (glass)
Light Travelling From
Optically Less Dense (air)into More Dense (glass)
When light travels from air to glass it bends towards the normal.

4. Optically Less Dense (air)into More Dense (glass)
Light Travelling From
Optically Less Dense (air)into More Dense (glass)
When light travels from air to glass it bends towards the normal.

5. Optically More Dense (glass) into Less Dense (air)
…..and Back Again
Light Travelling From
Optically More Dense (glass) into Less Dense (air)
When light travels from glass to air it bends away from the normal.

6. Optically More Dense (glass) into Less Dense (air)
……and Back Again
Light Travelling From
Optically More Dense (glass) into Less Dense (air)
When light travels from glass to air it bends away from the normal.

7. Optically More Dense (glass) into Less Dense (air)
……and Back Again
Light Travelling From
Optically More Dense (glass) into Less Dense (air)
When light travels from glass to air it bends away from the normal.

8. When light travels along the normal, it does not bend; it travels straight through. i = R = 0º The direction does not matter.

9. There no refraction at the arrow because the light is travelling along the normal. Therefore, it does not bend; it travels straight through.

10. When light travels toward a rectangular prism……

11. It first refracts from air i to glass.

12. It first refracts from air i to glass and bends toward the normal.

13. It then refracts from glass i to air and bends.

14. It then refracts from glass i to air and bends away from the normal.

15. Notice that since the prism is a rectangle, the first i is equal to the last R.
Therefore, the ray entering the prism is parallel to the ray leaving the prism.

16. The rays are said to be “Laterally Displaced”.

17. How does the depth and size of the fish appear?

18. Does the depth of the fish appear:
deeper?
the same?
shallower?

19. Two eyes have better depth perception than just one.
As light rays travel from the water to the air, they refract.

20. Two eyes have better depth perception than just one.
As light rays travel from the water to the air, they refract away from the normal.

21. The cat sees the refracted rays as originating closer to the surface.
Therefore, the fish appears to be shallower.

22. Does the fish appear:
larger?
the same?
smaller?

23. Apparent size is determined by the angle between rays entering the eye.
As light rays travel from the water to the air they……

24. Apparent size is determined by the angle between rays entering the eye.
As light rays travel from the water to the air, they refract away from the normal.

25. The cat sees the refracted rays with a larger angle between them.
Therefore, the fish appears to be larger.

26. How does the pencil appear?

27. The top of the pencil appears as any object would.

28. As light rays travel from the water to the air…….

29. As light rays travel from the water to the air, they bend away from the normal.

30. Ensure you look through the top of the surface.
The refracted rays make the bottom of the pencil appear larger and closer to the surface.

31. Why do the astronauts’ heads appear so small when they are underwater in a Neutral Buoyancy tank ?

32. Assume that the astronaut’s head is inside an air bubble.
Light rays from the astronauts’ heads are travelling from air (less dense) to water (more dense) and, therefore, refract.

33. Light rays from the astronauts’ heads are travelling from air (less dense) to water (more dense) and, therefore, refract toward the normal.

34. The light rays that enter the eye appear to come from a smaller head.

35. Fish Eye View
E3.4 explain the conditions required for partial reflection/refraction and for total internal reflection in lenses, and describe the reflection/refraction using labeled ray diagrams
What does a fish see when it looks up?

36. Fish Eye View
Think of light leaving the fish’s eye and incident to the surface. If the angle of incidence is greater than the Critical Angle (c), the ray totally reflects back into the water.

37. Fish Eye View
If the angle of incidence is less than the Critical Angle (c), the ray refracts out of the water.

38. Fish Eye View
Combining these two effects, light rays leaving the fish’s eye and incident to the surface would look like the image above.

39. Light rays are not intelligent. They cannot tell direction
Light rays are not intelligent. They cannot tell direction. Their paths can just be turned around. Therefore, the fish sees light coming from above as shown.

40. The light rays coming from above are extended back
The light rays coming from above are extended back. Recall our belief in “rectilinear propagation”.

41. If there are student swimmers in the class, they can observe this by diving into a pool and looking up. If you are lucky, they may even try to take a picture. Please share with me. .
The fish sees light coming from above as coming through a “hole” in the surface. The area around the hole acts like a mirror due to total internal reflection.

42. What does the left fish see when it looks at the right fish?

43. Light travels directly from the right fish to the left fish
Light travels directly from the right fish to the left fish. Therefore, it looks normal.

44. Think of light leaving the left fish’s eye and incident to the surface
Think of light leaving the left fish’s eye and incident to the surface. If the angle of incidence is greater than the critical angle (c), total internal reflection will occur. Anywhere to the right will act like a mirror as shown.

45. Therefore, there will be an image of the right fish above the surface.

46. The image of the right fish is seen by the left fish as usual
The image of the right fish is seen by the left fish as usual. Light rays appear to come from it directly.

47. The light rays must come from the right fish and reflect off the surface due to total internal reflection.

48. Note that the incident rays coming from the right fish do have an angle of incidence greater than the critical angle (c)

49. Note that the incident rays coming from the right fish do have an angle of incidence greater than the critical angle (c).

50. Try It - All you need is the following:
an aquarium filled with water,
a mirror held under water with an alligator clip on a stiff wire, and
a pencil.

51. Total Internal Reflection (TIR) is often used in quality periscopes, binoculars, and cameras.
This improves the performance of periscopes, binoculars, and cameras in low light conditions because no light is lost on reflection.

52. Recall that three mirrors arranged like the corner of a cube are called “Corner Cube Reflectors” or “retro reflectors”.
This is the principle used in bicycle reflectors.
E1.2 analyze a technological device that uses the properties of light (e.g., microscope, retro-reflector, solar oven, camera), and explain how it has enhanced society [AI, C]
The proof in three dimensions is beyond the mathematical ability level expected in this course.

53. In Corner Cube Reflectors, the incident ray and final reflected ray are parallel. They are in exactly opposite directions.
The light must reflect from each of the three mirrors.
E1.2 analyze a technological device that uses the properties of light (e.g., microscope, retro-reflector, solar oven, camera), and explain how it has enhanced society [AI, C]
The proof in three dimensions is beyond the mathematical ability level expected in this course.

54. If you look at the front of a reflector, notice that you see the reflection of where the mirrors meet (dotted line on the right image).

55. When you look at the front of a bicycle reflector - the hexagonal pattern of a Corner Cube Reflector can be seen.
Total Internal Reflection (TIR) is also used in Bicycle Reflector - Corner Cube Reflectors, because They are easy to mold and no light is lost in reflection.

56. If the protective backing of the reflector is removed, the back of the reflector appears to be a series of cubes.
The corners of these cubes can be felt.

57. Recall the proof in two dimensions that the initial incident ray and final reflected ray are parallel when two mirrors are connected at 90º.

58. Solid, molded plastic
Bicycle reflectors use molded plastic to make solid Corner Cube Reflectors.
Total Internal Reflection (TIR) occurs at the internal surfaces.
Solid, molded plastic Corner Cube Reflectors are easier to make, are more rugged, and better reflectors than tiny mirrors would be.
TIR
TIR

59. Total Internal Reflection (TIR) is also used in Fibre Optics.
When the incident ray enters the more optically dense material, it……

60. Total Internal Reflection (TIR) and Fibre Optics
When the incident ray enters the more optically dense material, it bends toward the normal as usual.

61. Total Internal Reflection (TIR) and Fibre Optics
When the ray moves from the more optically dense material to air, the angle of incidence is greater than the Critical Angle (c) and the light is totally reflected.

62. Total Internal Reflection (TIR) and Fibre Optics
This continues as the light ray travels through the fibre. The angle of incidence is greater than the Critical Angle (c) and the light is totally reflected.

63. Total Internal Reflection (TIR) and Fibre Optics
This continues as the light ray travels through the fibre. The angle of incidence is greater than the Critical Angle (c) and the light is totally reflected.

64. Total Internal Reflection (TIR) and Fibre Optics
This continues as the light ray travels through the fibre. The angle of incidence is greater than the Critical Angle (c) and the light is totally reflected.

65. Total Internal Reflection (TIR) and Fibre Optics
Notice that when the fibre is bent sharply, the angle of incidence is close to the Critical Angle (c) and may partly refract out of the fibre.

66. Total Internal Reflection (TIR) and Fibre Optics
Notice that when the fibre is bent sharply, the angle of incidence is close to the Critical Angle (c) and may partly refract out of the fibre.

67. As the ray approaches the last surface, the angle of incidence is less than the Critical Angle (c)
and the ray refracts out of the fibre bending away from the normal.

68. Fibre Optics (light) can carry much more information (band width) than traditional copper wire.

69. Why do cut diamonds sparkle so much?

70. Recall that diamond has a high index of refraction
Recall that diamond has a high index of refraction. As light enters diamond……

71. Recall that diamond has a high index of refraction
Recall that diamond has a high index of refraction. As light enters diamond, it bends more than when going into other materials.

72. It also results in diamond having a small critical angle
It also results in diamond having a small critical angle. This increases the likelihood of Total Internal Reflection (TIR) occurring in the diamond.

73. The carefully calculated shape of cut diamonds also increases the likelihood of any light entering to be reflected back out the top.

74. The carefully calculated shape of cut diamonds also increases the likelihood of any light entering to be reflected out the top.

75. Also recall that the high index of refraction of diamond causes large dispersion or separation of colours. The colours are even more widely separated due to multiple internal reflections.