# Lecture18 - Snell’s Law Total Internal Reflection Brewster’s Angle Dispersion Lenses Physics 102 Lecture 18 Phys 102 recent lectures •

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Unformatted text preview: Snell’s Law, Total Internal Reflection, Brewster’s Angle, Dispersion, Lenses Physics 102: Lecture 18 Phys 102 recent lectures • Lecture 14 – EM waves • Lecture 15 – Polarization • Lecture 20 & 21 – Interference & diffraction • Lecture 16 – Reflection • Lecture 17 – Spherical mirrors & refraction • Lecture 18 – Refraction & lenses ( today! ) • Lecture 19 – Lenses & your eye Light as a wave Light as a ray Snell’s Law: A Quick Review n 1 n 2 When light travels from one medium to another the speed changes v=c/n, but the frequency is constant. So the light bends: n 1 sin( θ 1 )= n 2 sin( θ 2 ) θ 1 θ 2 44 Total Internal Reflection normal θ 2 θ 1 n 2 n 1 Recall Snell’s Law: n 1 sin( θ 1 )= n 2 sin( θ 2 ) (n 1 > n 2 ⇒ θ 2 > θ 1 ) θ 1 = sin-1 (n 2 /n 1 ) then θ 2 = 90 θ c Light incident at a larger angle will only have reflection ( θ i = θ r ) θ i θ r 06 “critical angle” For water/air: n 1 =1.33, n 2 =1 θ 1 = sin-1 (n 2 /n 1 ) = 48.8 Fiber Optics 13 Telecommunications Arthoscopy Laser surgery Total Internal Reflection only works if n outside < n inside At each contact w/ the glass air interface, if the light hits at greater than the critical angle, it undergoes total internal reflection and stays in the fiber....
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## This note was uploaded on 01/25/2012 for the course PHYS 102 taught by Professor Lee during the Spring '08 term at University of Illinois, Urbana Champaign.

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Lecture18 - Snell’s Law Total Internal Reflection Brewster’s Angle Dispersion Lenses Physics 102 Lecture 18 Phys 102 recent lectures •

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