A beam of light of λ=600 nm from a distant source falls on a single slit 1 mm wide and the resulting diffraction pattern is observed on a screen 2 m away. The distance between first dark fringes on either side of the central bright fringe is

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(4) 2.4 mm. Given: λ=600 nm, a=1 mm, D=2 m. Idea: the two first dark fringes sit symmetrically about the centre, so the distance between them is twice the half-width. Half-width =(λ D)/a=(600×10⁻⁹×2)/(10⁻³)=1.2×10⁻³ m. Distance between them =2×1.2×10⁻³. =2.4×10⁻³ m. =2.4 mm.

A beam of light of λ=600 nm from a distant source falls on a single slit 1 mm wide and the resulting diffraction pattern is observed on a screen 2 m away. The distance between first dark fringes on either side of the central bright fringe is

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