Question

What is the distance between lines on a diffraction grating that produces a second-order maximum for 760-nm red light at an angle of 60.0º

Answer 1

The condition for maximum intensity is the same as that for a double slit. However, angular separation of the maxima is generally much greater because the slit spacing is so small for a diffraction grating. For a diffraction grating with lines/mm = lines/inch, the slit separation is d = micrometers = x10^ m.