lecture 25

# lecture 25 - 26.3 Total Internal Reflection Consider a...

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26.3 Total Internal Reflection onsider a light ray in air striking the surface of water: Consider a light ray in air striking the surface of water: art of the ray is refracted and part is Normal Part of the ray is refracted, and part is reflected. Air Water Incident ray Reflected ray θ i r The refracted ( R ) and reflected ( r ) angles will both change if we change e incident angle ( aw of Reflection Refracted ray R the incident angle ( Law of Reflection and Snell’s Law of Refraction ). Now consider what happens when a light ray emerges from a more dense medium into a less dense medium: water to air, for example.

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Part of the ray is reflected, and part is refracted. Air ater Notice that the refracted angle is greater than the incident angle since n air < n water . θ R Water Now let’s keep increasing the incident angle so that the refracted angle keeps increasing. i r c Notice: There is a point when the refracted angle = 90 o (red ray). his occurs when where This occurs when i = c , where c is known as the critical angle . Thus, when i = c , refracted = 90 0 . Now, if i > c , then there is no refracted ray (purple ray)! ll the incident light is completely t e cde t g t sco petey reflected back into the medium.
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## This note was uploaded on 08/04/2009 for the course PHYS 2002 taught by Professor Blackmon during the Spring '08 term at LSU.

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lecture 25 - 26.3 Total Internal Reflection Consider a...

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