For monochromatic light incident on a transmission grating, constructive interference occurs whenever the path difference between adjacent slits equals an integer multiple of the wavelength. Which of the following equations correctly relates the order number m, the wavelength λ, the grating spacing d, and the diffraction angle θ?
a) mλ=2dsinθ
b) mλ=dtanθ
c) mλ=dsinθ
d) mλ=sinθd