A certain diffraction grating has a groove density of 1200 lines/mm. These grooves extend over a distance of 5 cm. The grating is used to analyze the lasing emission occurring at A = 632.8 nm from a Helium-Neon laser.{a} If the laser beam is incident normal to the grating? at what angle dog the rst diffraction peak occur? What is the angular width of this peak if the grating is completely illuminated? {h} The HeliumwNeon Mer has a cavity length of 3|] cm so that its free spectral range {FER} is 50D MHZ. Thus? there are most likely several cavity resonances oscillating simultaneously, i.e., there could be three emission lines each separated from the next by the FER of the cavity. The grating discussed here cannot resolve these emission lines. How large would the grating need to be to just resolve the Mer lines? Use the Rayleigh criterion. {c} How large would the grating need to he to have a resolution comparable to a Fabry-Perot interferometer with a ll] cm cavity length [in air) and a nesse of 2m. {d} 'What key advantage does a grating have over a Fahry-Perot when used to analyse a laser spectrum? "What advantage does a Fahry-Perot have over a grating in the same situation