1. Refraction is the change in speed and change in direction* caused as light passes from one transparent media into another (* if incidence angle is not zero). You have all noticed how a stick seems to bend if it is immersed in water. Obviously, the stick does not bend, the light reflected from the immersed end bends as it leaves the water. Since we assume light comes in straight lines the position of the stick appears to change. In 1637, William Snell discovered the relationship between the incident angle and the refraction angle. The change in direction is dependent on the optical density of the two media. It would also be shown later that the optical density determined how the speed of light would change passing from one medium to another. Refraction of Light

2. The ratio of the speed of light in a vacuum to the speed of light in a transparent medium is called the index of refraction (n) n= index of refraction c= speed of light in a vacuum (3 x10 8 m/s) v = speed in medium e.g. Find the index of refraction of glass if the speed in glass is 2. 10 8 m/s

3. Materialn_____ Vacuum1.000… Air (at 20 o C)1.00029 Air (at 30 o C)1.00025 Water1.33 Ethanol1.36 Quartz1.46 Glass (crown)1.52 Glass (flint)1.61 Cubic Zirconia1.96 Diamond2.42

4. Snell’s Law William Snell showed that the change in direction of a ray of light that enters a new medium obliquely (θi not = 0 o ) is directly proportional to the sine of the incident and refraction angle. The proportionality constant is the index of refraction.

5. Incident medium Refractive medium boundary normal e.g. If a ray of light passes from air into glass with an angle of incidence of 40 o, find the angle of refraction

6. 1.00 sin 40 = 1.52 sin θ 0.643 = 1.52 sin θ 0.423 = sin θ Θ = 25 o

8. Critical Angle and Total Internal Reflection Light ray is totally reflected Diagrams below:Light going from water into air

9. Critical Angle The angle of incidence in the high density medium that produces an angle of refraction of 90 o

11. Applications and Examples of: Refraction, Critical Angel and Total Internal Reflection 1.Atmospheric Refraction: Sunset Effect

12. 1.Atmospheric Refraction: Heat Waves:

13. Mirage *Sun needs to heat surface * Surface must be dark and absorb heat * The air close to the ground becomes hotter than the air above. *Light from an object will refract. As it gets closer to the ground it will refract more and more horizontally until it exceeds the critical angle between warm and hot air and reflects off the boundary between the two layers of air *An observer will see the light coming from the ground and think the light has reflected off water on the road.

19. Periscope

23. Reflectors

24. Fiber Optics

30. Diamonds

39. http://famousdiamonds.tripod.com/cullinandiamonds.html

40. Section 2: Lenses Types of Lenses Converging Double Convex Plano Convex Meniscus Diverging Double Concave Plano Concave Meniscus

41. Geometry of Spherical Lenses

45. Applications of Lenses 1. Camera (case2 – small real image)

48. 2. Projectors (case 5, case 4) Overhead Projector

49. Slide Projector

50. Movie Projector

51. Persistence of Vision Human retina retains an image for a minimum of 1/20 s regardless of how long the image is visible If images are projected at a rate faster than 20 frames per second (fps), the motion looks continuous Movies are projected at 24 fps and TV at 30 fps http://www.colorado.edu/physics/2000/index.pl Animation: C:\AAABreen,Mike\PIX\Physics Pix\Light\Animation A common Movie or TV phenomena showing a car tire rotating in the “wrong” direction is caused by the strobing frequency of the movie being out of sync with the tire http://www.youtube.com/watch?v=qo1d6ttbAq8

52. Photocopier: case 3 – original size case 2 – reduced case 4 – enlarged

53. Telescope Astronomical Refracting

56. Telescope Astronomical Reflecting

60. Telescope Terrestrial Refracting

62. Microscope

63. Human Eye

64. HUMAN EYE --Very similar to the simple camera in operation. 1. Cornea -- transparent curved tissue that covers the front of the eye. Does most of the refraction of light entering the eye. 2. Aqueous Humour --transparent liquid that maintains the shape of the cornea. 3. Iris --colored part. system of muscles that regulate the size of the pupil. This process is called adaptation. 4. Pupil --black part. hole left by iris. 5. Lens -- flexible converging lens that changes its focal length allowing the eye to focus on objects that are at different distances. This process is called accommodation. Pupil dilating