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Unformatted text preview: PHYSICS 002C Lecture 16 May 6, 2009 Serway and Jewett Chapter 27 – Wave optics Summary of previous lecture: Given that : Light is a wave of the electromagnetic field that obeys the superposition principle because it is governed by a linear wave equation . Wave interference becomes totally spooky and inexplicable (in the sense that they are what they are, no more, no less) examples of wave- particle duality when we find out that they work for single particles of light (photons) when the intensity is turned way down. Wave optics is a straight forward application of Maxwell’s equations that we study wave optics to understand optical instruments and to be ready to appreciate the quantum world . Chap 27.1 – Conditions for interference Light beams interfere constructively or destructively when they overlap in time and space and their separate electric fields combine. Low intensity light waves pass through each other even though their electric fields are combined 2 1 E E + at the intersection because the wave equation is linear . Two light beams for which interference effects can be observed are said to be coherent . Otherwise the light is said to be incoherent . The coherence length L ∆ of the light source is the propagation distance over which the phase difference becomes random ϖ ∆ ≈ ∆ / c L . Interference effects with a laser illuminating a Michelson interferometer can be observed for path length difference of many meters. Chap 27.4 – Change of phase due to reflection....
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