  We derive from first principles the expression for the angular/wavelength
distribution of the intensity diffracted by a blazed reflective grating,
according to a scalar theory of diffraction. We considered the most common case
of a groove profile with rectangular apex. Our derivation correctly identifies
the geometric parameters of a blazed reflective grating that determine its
diffraction efficiency, and fixes an incorrect but commonly adopted expression
in the literature. We compare the predictions of this scalar theory with those
resulting from a rigorous vector treatment of diffraction from one-dimensional
blazed reflective gratings.
