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Home Optics Wave Optics Examples Spacing of the fringes at small angles | |||||
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Spacing of the fringes at small anglesAt small angles, we can use the approximation sin θ ≈ θ , which is valid if θ is measured in radians. The equation for double-slit diffraction becomes simply
which can be solved for θ to give
The difference in angle between successive fringes is the change in θ that results from changing m by plus or minus one,
For example, if we write θ7 for the angle of the seventh bright fringe on one side of the central maximum and θ8 for the neighboring one, we have
and similarly for any other neighboring pair of fringes.
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Home Optics Wave Optics Examples Spacing of the fringes at small angles |