Yellow sodium light, which consists of two wavelengths, λ_1 =589.0 nm and λ_2 = 589.89 nm, falls on a 7500 lines/cm diffraction grating. Determine (a) the maximum order m that will be present for sodium light, (b) the width of grating necessary to resolve the sodium lines, (c) the grating resolving power in this case, (d) the angular width of each sodium line.
The Attempt at a Solution
(a) I divided λ by Δλ and I found it to be 1000, therefore Nm, where m is the order, will be always larger than λ/ Δλ. therefore i don't get how the problem asks for maximum, however, m = 1 is an answer!
(b) I tried mλ = d sinθ but i don't know what θ to use !!
(c) it depends on (b)