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Principles of Physics

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Change in direction of light as it moves into a new medium and speed changes Only occurs if light enters medium such that 0˚< θ i < 90˚ θiθi θrθr θ r = angle of refraction

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Refraction can only occur when: there is a medium change the light enters at an angle between 0˚ and 90˚ When a toy car goes from tile to carpet such that both front wheels hit the carpet at the same time, the whole car slows down at the same time. A change in direction does not occur. When a toy car goes from tile to carpet at an angle. Each wheel hits the carpet at a different time. The first wheel to hit the carpet, slows down before the others causing the car to turn toward it.

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90˚ 1.To measure the angle place the protractor on the normal line facing the ray 2.Measure the angle from the normal line to that ray θiθi

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90˚ 1.To measure the angle place the protractor on the normal line facing the ray 2.Measure the angle from the normal line to that ray θrθr

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Determine the incident and refracted angles

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Ratio of the speed of light in a vacuum to the speed of light in other materials n= index of refraction (unitless) c = speed of light in a vacuum v = speed of light in material Greater n more the light slows down in the material

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Determine the speed of light in water if the index of refraction for water is 1.33

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Relates the index of refraction to the angle of refraction Dont forget ˚ is a unit!!!

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MaterialIndex Vacuum1 Air at STP Ice1.31 Water at 20 C1.33 Crown glass1.52 Salt1.54 Flint glasses1.66 Sapphire1.77 Diamond2.417 Corn oil1.47 Lucite1.5

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Determine the angle of refraction. n 1 = n air = 1.00 n 2 = n glass = 1.52 θ i = 30˚ θrθr crown glass θ 2 19˚

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θ c =critical angle: incident angle that causes refracted angle to be 90˚ in air

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Transparent materials can reflect. Total Internal Reflection: n high to n low θ i > θ c i ii θ i = θ r

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All wavelengths of light travel at 3x10 8 m/s in a vacuum In other materials each wavelength travels at a different speed In most materials red travels fastest and violet travels slowest Red is refracted least and violet is refracted most therefore the colors separate

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