Diffraction Grating Formula: d sin θ = n λ Steps: - Start with the diffraction grating equation: d sin θ = n λ, where d is slit spacing, θ is diffraction angle, n is order, and λ is wavelength. - Rearrange to n = (d / λ) sin θ, showing n is proportional to sin θ. - Plot n (y-axis) versus sin θ (x-axis) to get a straight line through the origin with slope (gradient) = d / λ. - Determine λ from the graph as λ = d / gradient, or equivalently λ = d × (1/gradient). Why B is correct: - Matches the rearranged equation n = (d / λ) sin θ, where plotting n vs. sin θ gives gradient = d / λ, so λ = d × (1/gradient) directly from the formula. Why the others are wrong: - A: Incomplete and does not specify axes or method to find wavelength. - C: Plots sin θ vs. n, yielding gradient = λ / d, so λ = gradient × d, not 1/gradient. - D: Includes d on …