Hi, I recently made a spectroscope using a pringles tube. I basically cut a very narrow slit at the metal end and at the plastic lid end I cut a circular shape out of a CD so that it fits inside the lid (I had to strip off the silver lining of course). I have some idea of how it works but would greatly appreciate some clarification and any extra information. Take the case of a sodium lamp that gives discrete spectral lines. As I understand it the light comes from the sodium lamp through the narrow slit and hits the CD inside the lid. The grooves on the CD reflect light at different angles depending on the wavelength which therefore split the light up. Since the silver surface is stripped off these reflected waves can transmit through into your eye. A couple of things I don't quite understand: 1) From what I have read, the reflected light rays can interfere constructively or/and destructively. So would you therefore not necessarily be seeing all the line spectra as some may have interfered destructively between the CD and your eye (if they were half a wavelength out of phase). 2) It also says that what you are seeing as line spectra are actually images of the slit. Is that right? Surely the light just comes through the slit, there's no image being formed is there?