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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 doubleslit 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 θ_{7} for the angle of the seventh bright fringe on one side of the central maximum and θ_{8} for the neighboring one, we have
and similarly for any other neighboring pair of fringes.


Home Optics Wave Optics Examples Spacing of the fringes at small angles 