I don't mean to violate any rules or conventions; these are questions pertaining to labs I'm doing as part of an undergrad degree. It's not homework, as such, so I've not put it in one of those forums But my apologies if this is incorrect. Anyhow; the experiment that bothers me is a spectroscopy one. Light is passesd through an optical fibre, through a bunch of mirrors and diffraction grating, and thence into a CCD. My questions being: what's electrical dark? Also, what's the 'noise' that I see in the spectrum? Is it some thermal effect on the CCD? Or is it something to do with the electrical dark? Indeed, is the electrical dark a thermal effect?