2010 PHYSICS 002C Lecture 14

# 2010 PHYSICS 002C Lecture 14 - PHYSICS 002C Lecture 14...

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PHYSICS 002C Lecture 14 April 30, 2010 Serway and Jewett Chapter 26.3-4 – Images formed by refraction DEMO 0 The magic upside down candle on the white board! Clicker Q1: A thin lens forms its image at the a) focal point; b) image point; c) object distance; d) fendipular fromawidget e) garthium ziparamus. Clicker Q2: An image of an external object formed inside of a convex curved surface of a thick transparent block is a) Real; b) Imaginary; c) Virtual; d) Vitreous; e) Complex. Clicker Q3: Which is not one of the axioms of geometric optics? a) at a reflecting surface the law of reflection governs the path of the rays; b) light rays travel in straight lines in a uniform medium; c) one may ignore diffractive effects; d) the Fraunhoffer index governs the path of the rays at an irregular interface; e) at a transparent surface the rays obey Snell’s law. DEMO 1 How thick does a crystal of Bismuth germinate appear to be? Chap 26.3 – Transmission through transparent surfaces Snell’s law – 2 2 1 1 sin sin n n can be used to trace rays through flat and curved transparent surfaces. The index of refraction is defined as 1 n 1 / / / vac f c v c n . How deep does the bottom of a crystal of index n 2 appear to be? By Snell’s law and geometry, 1 tan / q x and 2 tan / p x . Thus, 1 2 tan / tan p q . For small angles sin tan so 2 1 n p n q and q p n 2 in air. Rules of ray tracing: Light rays go in straight lines if the index of refraction is constant. Obey the laws of reflection ' 1 1 and refraction 2 2 sin 1 1 sin n relative to the local surface normal . n Rays converge and cross at a real image point. Rays appear to diverge from a virtual image point. Useful Corollary: Rays are undeflected or back-reflected if they are traveling normal to an interface.

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Ray Tracing for a curved transparent surface. (1) Draw the central ray from
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2010 PHYSICS 002C Lecture 14 - PHYSICS 002C Lecture 14...

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