diffraction grating

There was a question from Jerry in a previous post: "A simple question for which I can't find an answer: Why do you have to collimate light spectroscopy? What would happen if you didn't collimate it?" The basic idea of spectroscopy is to look at the different colors of light coming from some source. Typically light from a source (like an excited gas) is passed through a diffraction grating that makes different colors bend different amounts (like a prism, only better). Collimated light is basically light that is all going the same direction. How about I go ahead and draw a picture. This is…