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# 102 lect20_handout - Physics 102 Lecture 20 Interference Physics 102 Lecture 20 Slide 1 Phys 102 recent lectures Light as a wave Lecture 14 EM

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Physics 102: Lecture 20, Slide 1 Physics 102: Lecture 20 Interference

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Physics 102: Lecture 20, Slide 2 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 Lecture 19 – Lenses & your eye Light as a wave Light as a ray
Physics 102: Lecture 20, Slide 3 Superposition t +1 -1 t +1 -1 t +2 -2 + Constructive Interference In Phase

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Physics 102: Lecture 20, Slide 4 Superposition t +1 -1 t +1 -1 t +2 -2 + Destructive Interference Out of Phase 180 degrees
Physics 102: Lecture 20, Slide 5 ACT: Superposition + Different f 1) Constructive 2) Destructive 3) Neither -1.5 -1 -0.5 0 0.5 1 1.5 -1.5 -1 -0.5 0 1

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Physics 102: Lecture 20, Slide 6 Interference Requirements • Need two (or more) waves • Must have same frequency • Must be coherent (i.e. waves must have definite phase relation)
Physics 102: Lecture 20, Slide 7 Demo: Interference for Sound … For example, a pair of speakers, driven in phase, producing a tone of a single f and λ : l 1 l 2 But this won’t work for light--can’t get coherent sources hmmm… I’m just far enough away that l 2 - l 1 = λ /2, and I hear no sound at all!

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Physics 102: Lecture 20, Slide 8 Interference for Light …
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## This note was uploaded on 02/05/2012 for the course PHYS 102 taught by Professor Carruba during the Spring '09 term at University of Illinois at Urbana–Champaign.

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102 lect20_handout - Physics 102 Lecture 20 Interference Physics 102 Lecture 20 Slide 1 Phys 102 recent lectures Light as a wave Lecture 14 EM

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