College Physics 10th Edition by Raymond Serway,Chris Vuille

Exercise 19

Take red light at 700 nm and violet at 400 nm as the ends of the visible spectrum and consider the continuous spectrum of white light formed by a diffraction grating with a spacing of d meters between adjacent lines. Show that the interval v 2 r 2 of the continuous spectrum in second order must overlap the interval v 3 r 3 of the third-order spectrum. Note: v 2 is the angle of the violet light in second order, and r 2 is the angle made by red light in second order.