:QUOTE [quotetype:personal] A diffraction grating and a camera is all it takes to see what light is made of. :INFO How a Simple Spectrometer Works A spectrometer splits light into its component wavelengths using a diffraction grating — a surface with microscopic parallel lines that diffracts different wavelengths at different angles. A CD or DVD cut into a strip works as a grating. Light enters through a narrow slit, diffracts off the grating, and projects a rainbow spectrum onto a detector (a webcam or camera sensor). Free software (Spectral Workbench) calibrates and reads the spectrum. :COUNTER.half 400 to 700 nm | :COUNTER.half 0.1 to 1 nm :PATH Build the Enclosure and Slit Cut a narrow slit in a cardboard box — 0.5mm is the target width. | :INFO Build the Enclosure and Slit Cut a narrow, straight slit in one end of a light-tight cardboard box using a razor blade and metal ruler. Target 0.5mm width — wider means lower spectral resolution, narrower means less light. Line the interior with matte black paper or paint to prevent internal reflections. Mount the box on a stable surface with the slit pointing toward your light source. :PATH Cut and Mount the DVD Grating Cut a strip from a DVD, remove the reflective layer, and mount at an angle. | :INFO Cut and Mount the DVD Grating Cut a 2cm strip from a standard (not Blu-ray) DVD. Remove the reflective aluminum layer by peeling it away from the transparent polycarbonate — this leaves a clear grating. Mount the clear grating strip at the opposite end of the box from the slit, angled at approximately 45 degrees. The webcam looks through or alongside the grating. :PATH Mount the Webcam and Capture Spectra Point the webcam at the grating and capture the diffracted spectrum. | :INFO Mount the Webcam and Capture Spectra Mount a webcam looking through the end of the box at the grating. The diffracted spectrum will appear as a rainbow stripe in the camera image. Use Spectral Workbench (spectralworkbench.org) or RSpec software for calibration and analysis. Calibrate using a known light source — a compact fluorescent lamp has sharp emission lines at known wavelengths. :CHECKLIST What You Need [ ] Old DVD (not Blu-ray) [ ] Cardboard box — shoeboxes work well [ ] Webcam or USB camera [ ] Razor blade and metal ruler for the slit [ ] Matte black paint or paper for interior [ ] Spectral Workbench (free, web-based) :NOTE Calibration Makes the Difference An uncalibrated spectrometer shows a rainbow but cannot tell you wavelengths. Calibrate by capturing a compact fluorescent (CFL) bulb spectrum — CFLs have sharp mercury emission lines at precisely known wavelengths (435.8nm, 546.1nm, 611.6nm). Set these peaks in your software and the wavelength scale calibrates automatically across the visible range. :QUOTE [quotetype:personal] The same tool, scaled up, tells us what distant stars are made of. Your version works on the same principle. :LINK https://spectralworkbench.org/wiki/diy-spectrometer Public Lab — DIY Spectrometer Build Guide