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I've seen other answers on stack exchange for this question, but none of them seem to give an intuitive explanation.

Is there an explanation that takes a more intuitive approach (if possible, not involving QM)?

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The fringe pattern is analogous to the sinc function transmit/receive beam pattern from a monochromatic aperture. In these the side lobe angular spacing is determined by the change in transmit/receive angle needed to cause one wavelength difference in the total travel path. However as that angle approaches zero for the main lobe, the pattern instead of approaching zero approaches unity because of sin x tending to x. The process repeats on the other side as the angle passes zero except the the pattern is reversed. This causes the main lobe to be twice as wide as the side lobes.

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  • $\begingroup$ could you explain why it can be modelled by the sinc function? $\endgroup$
    – XXb8
    Commented Apr 16, 2020 at 18:20
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    $\begingroup$ Hard to simply explain. Imagine sinusoidal plane waves impinging on a linear aperture from an angle that can be varied. Imagine also that the aperture sums up everything that impinges on it and that is the output of the aperture. As the angle changes from 0 ('boresight') degrees to 90 degrees ('endfire') the induced distribution across the aperture changes from a time varying constant to a time varying sinusoid, and integrating the distribution across the aperture yields a sinc function as a function of arrival angle with the spatial wavelength as a parameter. $\endgroup$
    – user45664
    Commented Apr 16, 2020 at 20:08

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