Single-Aperture Interference When coherent light shines through a single small slit onto a screen, the multiple slit diffraction equation ( 2 l sin θ = N λ ) fails to predict the maxima and minima. The first problem is that l was used to describe the distance between the slits, but now there is only one. Next, the central bright fringe is roughly three times wider than all the other maxima, which drop off in intensity very rapidly as shown. Clearly, the light is undergoing interference, but some adjustments will be needed if a simple equation is still going to be used to describe it. The solution is to use exactly the same equation with three critical concessions: First, l now describes the width of the slit itself. Second, odd values of N now describe maxima and even values describe minima. (This may be easier to remember if one bears in mind that a single slit is an odd number, even though this implies that all numbers greater than one are even.) Third, zero will no longer be allowed as a valid number. That is, the entire central maximum will be
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This note was uploaded on 04/05/2012 for the course PHYS 131 taught by Professor Tibbets during the Spring '11 term at Cuyamaca College.