 Solution

ID: past-exam-of-the-physics-course-of-the-year-4-of-the-natural-sciences-course-of-the-university-of-cambridge/2014/paper-1/b7/a/solution

The relative slit-centre phase is

2 π d sin θ / λ

. Near the optical axis,

x ≃ L θ

, so adjacent interference maxima have spacing

δ x ≃ \frac{λ L}{d} = \frac{L}{1000} .

Slow diffraction-envelope variation can slightly shift the exact local maxima.

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