A beam of wavelength λ passes through a single slit of width a and produces its first dark fringe at a small angle θ from the central maximum on a distant screen. If the slit width is doubled to 2a while the wavelength remains the same, what happens to the angular position θ′ of the first dark fringe? (Assume θ and θ′ are small enough that sinθ≈θ.)
a) θ′≈2θ
b) θ′≈2θ
c) θ′≈θ
d) θ′≈4θ