Figure 3-47 A Grating Spectrograph (a) The diffraction grating in a grating spectrograph has many parallel lines on its surface that reflect light of different colors in different directions. This separation of colors (wavelengths) allows the object’s spectrum to be analyzed. (b) This peacock feather contains numerous natural diffraction gratings. The role of the parallel lines etched in a human-made diffraction grating is played by parallel rods of the protein melanin in the feathers. (c) CDs and DVDs store information on closely spaced bumps located on a set of nearly parallel tracks. Light striking these tracks systematically reflects different colors in different directions—a CD or a DVD behaves like a diffraction grating.