Module 4, Week 13 Activity 3: The Diffraction Grating K L central 2 axis A diffraction grating is to be used to analyze a light source of unknown wavelength. The grating spacing is unknown, so the diffraction grating is first calibrated with a 680 nm red laser beam. The laser's first bright fringe below the central maximum is observed at y = 5 cm below the central axis on a screen placed L = 25 cm from the grating. After calibration, the unknown light source is directed through the diffraction grating, and a bright spot is observed exactly 4.18 cm above the central axis. 1) What is the wavelength of the unknown source? Big Ideas: Refraction Polarization Justification: Text