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Unformatted text preview: 1 Lecture-25 Double-Slit Interference Intensity Profile , including Diffraction Interference fringes result from two diffracted intensities from two identical slits. Note L >> d. Diffracted light from each slit of width a is where At point P at , total E is sum of E 1 and E 2 . But the two beams are out of phase by : The sum is Therefore, amplitude of sum E-field is Or, 2 cos 2 / 2 / sin 2 E E sin cos sin sin sin 2 2 d a a I I 2 / 2 / sin ) 2 ( 1 o or E E t E E sin 2 cos 2 10 E E , where sin 2 a : Diffraction sin 2 d : Interference a d sin E 1 E 2 2 @ larger slit width @ smaller slit width Interference fringes of two sets of double-slits Diffraction fringe from single slit S 1 Interference fringes from two undiffracted intensity fields Interference fringes from...
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