Lec23-1

# Lec23-1 - ture 23-1 ture Review Laws of Reflection and...

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cture 23- cture 23- 1 Review: Laws of Reflection and Refraction Law of Reflection A reflected ray lies in the plane of incidence The angle of reflection is equal to the angle of incidence 1 1 θ = Law of refraction A refracted ray lies in the plane of incidence The angle of refraction is related to the angle of incidence by 2 2 1 1 sin sin n n = Snell’s Law Medium 1 Medium 2 2 1 n n / 1 i i i i c n c f f n n λ = = = × Where λ is the wavelength in vacuum

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cture 23- cture 23- 2 Demo 7A-05 Candle Illusion
cture 23- cture 23- 3 Total Internal Reflection In general, if sin θ 1 > ( n 2 / n 1 ), we have NO refracted ray; we have TOTAL INTERNAL REFLECTION . All light can be reflected, none refracting, when light travels from a medium of higher to lower indices of refraction. e.g., glass (n=1.5) to air (n=1.0) 1 sin sin 2 1 1 2 = n n θ 2 1 But θ 1 cannot be greater than 90 degrees ! ( 29 1 2 1 sin / c n n - Critical angle above which this occurs. medium 2 medium 1

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cture 23- cture 23- 4 ©2008 by W.H. Freeman and Company
cture 23- cture 23- 5 Examples 1 1 sin 48.8 1.33 c θ - = ° ÷ Fish’s view of the world Prism used as reflectors Optical fiber 1 1.33 sin 62.5 1.5 c - = ° ÷ in water 1 1 sin 41.8 1.5 c - = ° ÷ in air (e.g., glass with n=1.5) 1 1 sin 41.8 1.5 c - = ° ÷ (e.g., glass with n=1.5)

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Lec23-1 - ture 23-1 ture Review Laws of Reflection and...

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