Introduction and Objectives

Spectrophotometry is one of the most fundamental and widely used analytical techniques in modern science. By measuring how much light a substance absorbs at different wavelengths, it enables the quantitative characterization of chemical compounds in fields as diverse as chemistry, biology, medicine, and environmental monitoring. In particular, UV-visible (UV-Vis) absorption spectrophotometry is built on the Beer-Lambert law, which states that the amount of light absorbed by a solution is proportional to the concentration of the absorbing substance. This makes it an indispensable tool in both research and educational settings, where it underlies experiments ranging from the quantification of biomolecules to the study of reaction kinetics [1].

Despite its importance, access to absorption spectrophotometry is far from universal. Commercial UV-Vis spectrophotometers, while offering excellent performance, are expensive instruments that many schools and universities, particularly those with limited budgets, cannot afford [2]. Beyond the financial barrier, modern commercial instruments present a further challenge in educational contexts: they function as so-called "black boxes", hiding from the user the physical principles that underlie the measurement. Students who interact only with polished commercial devices are often left with little understanding of how a spectrum is actually generated, what role the diffraction grating plays, or why alignment and calibration matter [3][6]. This gap between instrument use and instrument understanding is a genuine obstacle to deep learning in physics and chemistry education.

In response to these challenges, a growing body of work over the past two decades has explored the construction of low-cost, home-built spectrophotometers for educational use. These range from very simple devices assembled from compact discs, flashlights, and cardboard [5], to more refined systems built from LEGO bricks [7][8], 3D-printed parts [3], or smartphone platforms [4]. A common finding in this literature is that building an instrument from scratch (selecting components, aligning optics, calibrating the wavelength scale, and troubleshooting) provides a qualitatively richer learning experience than simply operating a commercial device. Students who build their own spectrophotometers develop a hands-on understanding of diffraction, Beer-Lambert behavior, and sources of experimental error that would otherwise remain abstract [6][8]. At the same time, these devices can bring quantitative spectroscopic measurement within financial reach of institutions that would otherwise have none [5].

\bigskip\noindent The present thesis is situated within this context. Its central aim is the design, construction, and characterization of a low-cost absorption spectrophotometer intended primarily for educational use. The instrument is developed with transparency in mind: every component is chosen and arranged so as to make the underlying physics as visible and understandable as possible to anyone assembling or using it. Alongside the hardware, a dedicated software system is developed to handle data acquisition, wavelength calibration, and the computation of absorbance spectra.

More specifically, the thesis begins by reviewing the theoretical foundations of UV-Vis absorption spectroscopy, including the Beer-Lambert law and the general operating principles of spectrophotometric instruments. It then surveys existing low-cost and DIY spectrophotometer designs from the literature, identifying key design choices and their trade-offs. The bulk of the work describes the hardware and software of the constructed instrument in detail, including the practical obstacles encountered and the solutions adopted. Finally, the performance of the device is validated through experimental measurements, and its limitations and potential improvements are discussed.

By addressing these objectives, this thesis aims to contribute to the broader effort of making spectroscopic measurement accessible, transparent, and educationally meaningful — an effort that is increasingly recognized as valuable not only in chemistry, but in physics education as well [3][6].