Students learned the principles and practice of photometry through project-based learning. They addressed the challenge of measuring the unknown concentration of a colored substance using a photometer they were required to design, build, and test. Then, they used that instrument to carry out the experiment and fulfill the challenge. A photometer was designed and built by students consisting of a green laser pointer as the light source and a lux meter as the detector and readout. Using this photometer students have determined the concentration of the unknown sample of KMnO[subscript 4] solutions. The concentration of this sample solution was calculated to be (4.62 ± 0.06) × 10[superscript -4] M; this value agrees within 6% of the expected value from the measurement using the commercial spectrophotometer which was calculated to be (4.96 ± 0.005) × 10[superscript -4] M. The experiments fit well into an analytical chemistry course and take a standard (1 h) lab period. This project has facilitated improved student understanding of the photometry concepts and increased the creative problem-solving. In general, the students' response to this laboratory was positive.