394 Interference of Light WavesP37.38The condition for bright fringes is22tnmn+=λλm=123,,,….From the sketch, observe thattRRRrRrR=−≈−+FHGIKJ=FHGIKJ=111222222cosθaf.The condition for a bright fringe becomesrRmn212FHGIKJλ.Thus, for fixed mand ,nr2=constant .Rr tFIG. P37.38Therefore, nrnrfiliquidair=andnliquidcmcm==10015013122....af.P37.39For destructive interference in the air,2tm=.For 30 dark fringes, including the one where the platesmeet,t×−29 6002870 106nmmaf..Therefore, the radiusof the wire isrt=2870435..m2mµ.FIG. P37.39P37.40For total darkness, we want destructive interference for reflected light for both 400 nm and 600 nm.With phase reversal at just one reflecting surface, the condition for destructive interference is
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This note was uploaded on 12/14/2011 for the course PHY 203 taught by Professor Staff during the Fall '11 term at Indiana State University .