A 5.000-cm-wide diffraction grating with 200 slits is used to resolve two
closely spaced lines (a doublet) in a spectrum. The doublet consists of two
wavelengths, \(\lambda_{\mathrm{a}}=629.8 \mathrm{nm}\) and
\(\lambda_{\mathrm{b}}=630.2 \mathrm{nm} .\) The light illuminates the entire
grating at normal incidence. Calculate to four significant digits the angles
\(\theta_{1 \mathrm{a}}\) and \(\theta_{\mathrm{lb}}\) with respect to the normal
at which the first-order diffracted beams for the two wavelengths,
\(\lambda_{\mathrm{a}}\) and \(\lambda_{\mathrm{b}}\), respectively, will be
reflected from the grating. Note that this is not \(0^{\circ} !\) What order of
diffraction is required to resolve these two lines using this grating?