Answer:
C- ±37.6°
Explanation:
This is the case of a single slit diffraction. In this case, the dark fringe occurs at
sin θ = ± mλ/a
where m = 1
θ = ± 30°
Hence we have sin ± 30° = ± λ/a
±0.5 = ± λ/a
Hence, we have a = 2λ
For a circular aperture, the condition for the first dark fringe is
D = diameter of circle = a = 2λ
so we have sin θ1 = 1.22λ/a
sin θ1 = 1.22λ/2λ
hence sin θ1 = 0.61
θ1 = sin⁻¹0.61 = ±37.6°
