Warm-up: The index of refraction for acetone is 1. 36 Warm-up: The index of refraction for acetone is 1.36. What is the speed of light in acetone? Vacetone = ?

Total Internal Reflection

Describe the relationship between the refraction index of a medium and the speed of light passing through that medium. As the index of refraction increases, the speed of light slows down. For example, light moves slower in acrylic than quartz. Medium n Vacuum/space and Air 1.00 Ice 1.31 Water (pure) 1.33 Ethyl alcohol 1.36 Quartz 1.46 Vegetable oil 1.47 Olive oil 1.48 Acrylic 1.49 Glass 1.52 Diamond 2.42

Draw and label a ray diagram of light moving from water to air.

Light bends away from the normal when it speeds up at the boundary of two medium, (ie from water to air). In this situation the angle of refraction is larger than the angle of incidence. Critical angle Eventually the angle of refraction will increase so it is 90o. The angle of incidence that produces an angle of refraction of 90o is the critical angle.

Total internal reflection If you increase the angle of incidence PAST the critical angle, the refracted ray will no longer exit the medium. Instead it will reflect back into the medium. The refracted ray will disappear and only a reflected ray is visible. Total internal reflection: When the angle of incidence is greater than the critical angle

When light travels from slower to faster medium…. Option 1: -Incident angle < critical angle -Ray is refracted into air Option 3: -Incident angle > critical angle -Ray reflected internally Option 2: -Incident angle = critical angle -Ray refracted at 90o

Draw a ray diagram of light as it moves through a diamond Diamonds are cut to take advantage of their critical angle of 24.4. A properly cut diamond will sparkle more because the light reflects out the top of the diamond.

Review… Fiber optic Cables: How they work https://www. youtube Review… Fiber optic Cables: How they work https://www.youtube.com/watch?v=0MwMkBET_5I Making fiber optic wire https://www.youtube.com/watch?v=u1DRrAhQJtM

Practice: Complete rest of worksheet -Questions 1, 2, 8 Wednesday: QUIZ! 1) Images in plane mirrors 2) Images in convex and concave mirrors 3) Index of refraction and speed of light