Chapter 10: Problem 3
The Bragg equation (10.10.13) is similar in form to the grating equation (10.8.10) with \(\theta_{\phi}=\theta_{2}\) However, for the grating the angles \(\theta_{\alpha}, \theta_{\theta}\) are measured from the normal, whereas in the Bragg case the angle \(\theta\) is measured, by convention, from the diffracting planes in question (rather than from the normal to the planes). What is the relation between the two situations? Why not use the cosine in place of the sine in one equation, since the angles appear to be complements?