A diffraction grating has resolving power R = ?avg/?? = Nm. (a) Show that the corresponding frequency range ?f that can justbe resolved is given by ?f = c/Nm ?. (b) From Fig. 36-22, show that thetimes required for light to travel along the ray at the bottom of thefigure and the ray at the top differ by ?t = (Nd/c) sin ?. (c) Show that(?f )(?t) = 1, this relation being independent of the various gratingparameters. Assume N »1.