In an effort to make chemistry and physics instrumentation available to high school and introductory college chemistry and physics classes, we have developed simple spectrophotometers that can be constructed using readily available parts at extremely low cost ($25). One design is constructed using Lego® blocks, a light emitting diode, and optical elements including a lens, slide-mounted diffraction grating, and photodiode detector. The photodiode detector is mounted on a rotatable arm for wavelength selection based on simple laws of diffraction. The design is extremely simple, thereby demonstrating basic physical principles (such as diffraction and absorption of light) that are frequently lost in commercial “black box” instruments. Performance, measured by comparison to a commercial spectrometer, is sufficiently quantitative to facilitate experiments such as the determination of the pKa of an acid-base indicator! Our publication in J. Chemical Education can be viewed here: 55-162xt6c Supplementary information useful to those constructing the spectrometer can be found here:55supp-2cih6ac
Molecular Reaction Dynamics