Diffraction is a phenomenon that occurs when a wave, such as light or sound, encounters an obstacle or a slit that bends the wave and spreads it out. The two main conditions under which diffraction takes place are:
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The wavelength of the incident wave should be comparable to the size of the obstacle or slit.
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The incident wave should have a coherent phase, meaning that the wave's phase at any given point in space and time is well-defined.
Now, let's represent the diffraction pattern due to a single slit with a ray diagram and the fringe pattern formed on the screen.
Ray Diagram:
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Start with a plane wavefront (parallel light rays) incident on a single slit of width 'a' on a barrier.
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As the light passes through the slit, it diffracts, and the wavefront starts spreading out.
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Draw rays from the slit to the screen placed at a distance 'D' from the barrier. The rays should fan out from the slit.
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On the screen, mark the central maximum (bright fringe) at the center of the screen, where the light rays are focused.
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On either side of the central maximum, draw minima (dark fringes) at locations where destructive interference occurs.
Fringe Pattern:
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On the screen, the intensity of the diffracted light forms a fringe pattern, with a bright central maximum at the center.
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The intensity of the light decreases as you move away from the central maximum.
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The minima (dark fringes) occur at locations where destructive interference takes place, and the intensity is zero.
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Between the minima, secondary maxima occur, with decreasing intensity as you move away from the central maximum.
The diffraction pattern due to a single slit can be explained by Huygens' principle and the interference of the diffracted waves. You can find more detailed information in textbooks or online resources on optics or wave physics.
