Interference & DiffractionDefinitionsAgainColorSlide 5Remember Huygens‘ Principle?A long distance from the center you have a plane wave approximation.Adding WavesSlide 9Slide 10Interference and DiffractionYoung’s Experiment (Double Slit Expt.)Staying Young (R>>d)Overview of Young’s Thingy (What is l?)Ye olde oil slickAn inconvenient fact: Phase shifts on reflection:NO phase change at (b) or (d)Newton’s RingsTesting a LensAnti-reflective coatingsInterference & DiffractionChapter 26DefinitionsMonochromaticLight Waves of one wavelength, orA single color (same thing)PolychromaticMany wavelengthsWhite LightA mixture of all colorsAgainColorLightOOO..It’s Red!RememberHuygens‘ Principle?A long distance from the center you have a plane wave approximation.Adding WavesIn PhaseIn PhaseThis is calledCONSTRUCTIVEInterferenceDestructiveInterferenceInterference and DiffractionEverything is based upon how separate waves interact with each other, usually a long distance from the source.Huygen’s principle applies.These waves addConstructively … they produce a bright intensityDestructively … they produce a dark band where little light appears.Young’s Experiment (Double Slit Expt.)LightSourceProducesa small regionwhich mimicsa coherentlight sourceThe lightfrom S1 &S2 arein-phaseThe rays add upto produce brightand dark bands where raysfrom S1 and S2 are in or out of phase when theyget to the screenStaying Young (R>>dR>>d))sin( ) Bright Band1sin( ) ( ) Dark Band2d md mq lq l== +r1 and r2 are PARALLEL!!Overview of Young’s Thingy(What is ?)4 7sin 39.490.0095 1000sin0.2 0.0095 / 336.3 10 6.3 10 633dmmradmmdmm m nmq lqqll- -== == = �= � = � =Ye olde oil slickAn inconvenient fact: Phase shifts on reflection:No shiftNo shiftshift of shift of /2/2HmmmmNO phase change at (b) or (d)Newton’s RingsTesting a LensAnti-reflective
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