# 3-slit diffraction

For three parallel slits of equal size and with neighbor to neighbor distances being $$a$$ and $$b$$, respectively. The intensity at diffraction minima is zero, if $$\dfrac{a}{b} = \dfrac{n}{m}$$, where $$n$$ and $$m$$ are positive integers when a plane wavefront of light perpendicular to slits illuminates them.

Which of the following is a possible value of $$n-m$$?

Assume that we ignore single slit diffraction.

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