The true colours of white light: hands-on optical spectrometry
  Although the observation of optical spectra is common practice in physics classes, students are usually limited to a passive, qualitative observation of nice colours. This article discusses a diffraction-based spectrometer that allows students to take quantitative measurements of spectral bands. Students can build it within minutes from generic low-cost materials. The spectrometer's simple, didactic design allows students to fully comprehend the underlying physical concepts and to engage in a discussion on measurement errors and uncertainties. 
Robert Fischer
physics.ed-ph