Diffraction By Slits

Diffraction By Slits - FRAUNHOFER DIFFRACTION The...

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Unformatted text preview: FRAUNHOFER DIFFRACTION The diffraction from slits of a range of widths is depicted in Fig. 1. D«x a>x Fig. 1 Intensity distribution behind an aperture of width a = A (left), a very small aper- ture (center), and a large aperture (right). The Fraunhofer diffraction by a single slit is shown in Fig. 2. s Fig. 2 (a) Franhofer diffraction by a slit. (b) Diffraction pattern at infinity but focused to nearby plane. Fraunhofer Diffraction — Fourier Transform The Fraunhofer diffraction pattern (in amplitude as opposed to intensity) of an aperture is the Fourier transform of the amplitude transmittance function of that aper- ture. The Fraunhofer (far-field) diffraction intensity pattern for a single slit is given by 1 = 10 [LWMST‘U] 2 sinO A 7T0, This is shown in Fig. 3. Plot of amplitude and intensity I I l | I Amplitude : / l I l I I I 2 I I I I I I I 0} I I I I I I \ I I l Fig. 3 Fraunhofer diffraction pattern for a single slit. The effect of increasing the number of slits is shown in Fig. 4. (a) D i o_________.________-__-___ T l A/D sin a l .......... N firm. (b) L ' . 0- -_b. _H- -»-:.+_~.:z I “““““ fin; ........ __ (c) I . 0 M. .... .. 3"" . ~ — - 5 ~ 9 — How—uh— I I ------------ h 5",; .... N ' . ------ a 3‘". I ‘s - ._ A , '. . . i o X/d 2nd 3M1 4M1 sin 9 Fig. 4 Fraunhofer diffraction patterns for one, two, three, and four slits. FRAUNHOFER DIFFRACTION PATTERNS (a) Fraunhofer diffraction pattern of a single slit. (b), (c), (d), (e) Interference patterns of 2, 3, 4, and 5 slits respectively. The slit systems are indicated on the left. ...
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This note was uploaded on 04/29/2008 for the course ECE 4500 taught by Professor Gaylord during the Spring '08 term at Georgia Tech.

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Diffraction By Slits - FRAUNHOFER DIFFRACTION The...

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