Let us consider the secondary waves travelling in a direction inclined at an angle φ with the initial direction of the incident light. Or As θ is small Thus, the angular separation between any two consecutive minima (or maxima) is equal to The angular separation is inversely proportional to (a+b), the distance between two slits. From equation (II) we get andħ INTERFERENCE MAXIMA AND MINIMA (contd.): corresponding to the directions of the maxima can be obtained. corresponding to the directions of minima can be obtained.ĥ INTERFERENCE MAXIMA On the other hand if the secondary waves travel in a direction such that the path difference is even multiple of, gives the direction of the maxima due to interference of light waves from the two slits.Ħ INTERFERENCE MAXIMA AND MINIMA (contd.): From the triangle CANĤ INTERFERENCE MINIMA If the path difference is equal to odd multiple of, θ gives the direction of minima due to interference of the waves from the two slits. INTERFERENCE MAXIMA AND MINIMA: Let us consider the secondary waves travelling in a direction inclined at an angle θ with initial direction. Therefore point P corresponds to the position of the central bright maximum. All the secondary waves travelling in a direction parallel to OP come to focus at P. Let a plane wave front be incident on the surface XY. Lens L is placed between slits and the screen, focuses the interference-cum-diffraction pattern on the screen.ģ FRAUNHOFFER DIFFRACTION AT DOUBLE SLIT (contd.) The width of each slit is ‘a’ and are separated from each other by opaque portion whose width is ‘b’. So, the resultant pattern on the screen will consists of: 1) Interference pattern due to two slits 2) Two diffraction patterns, one due to each slitĢ FRAUNHOFFER DIFFRACTION AT DOUBLE SLIT (contd.)Ĭonsider two rectangular slits AB and CD parallel to each other and perpendicular to the plane of paper. Each slit also produces a diffraction pattern of its own. While dealing with interference, we considered the interference of the secondary waves originating from the two slits. Presentation on theme: "FRAUNHOFFER DIFFRACTION AT DOUBLE SLIT"- Presentation transcript:
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