An easy-to-build optical spectrometer for the Rayleigh scattering investigation of coffee solution

Abstract

Spectroscopy is an essential technique required in numerous analytical fields, yet spectrometers are often expensive instruments. In this study, we present an easy-to-build and low-cost optical spectrometer. The spectrometer is constructed from readily accessible materials including a white LED as the light source, a collimating lens, a cuvette, a slit, a DVD as the diffraction grating, and a webcam. This device is designed to measure the visible light spectra of liquid samples, which could then be processed into transmittance, absorbance, and spectral intensity graphs. We took measurements from several absorbing and scattering samples to evaluate the designed spectrometer. We chose solutions of food colouring as an absorbing medium and instant coffee as a scattering medium. We showed that instant coffee is a very good candidate for Rayleigh scattering experiments, and that the relative concentration of coffee can be investigated by these experiments.