Measuring Wavelengths with a CD A laser beam of wavelength = 632.8 nm shines at normal incidence

Question:

Measuring Wavelengths with a CD A laser beam of wavelength λ = 632.8 nm shines at normal incidence on the reflective side of a compact disc. The tracks of tiny pits in which information is coded onto the CD are 1.60µm apart. For what angles of reflection (measured from the normal) will the intensity of light be maximum?