Building a Custom Microscope – An advanced lab to study Brownian motion

The process of building a microscope from scratch provides the students with a basic understanding of each individual component of the optical set-up. Subsequent digital image recording and data analysis provide an introduction to image processing and statistical analysis. Our goal is to create an advanced laboratory module for students to build an optical microscope, calibrate it, and make precise measurements of Brownian motion. We constructed an optical microscope based on the design by Kemp et al. (arXiv:1606.03052). Then, using a 40x objective, we study the Brownian motion of 1 micron colloidal particles. A digital camera is used to record videos of colloidal motion, ImageJ is used to post-process the images, and Matlab is used to calculate the diffusion coefficient of the particles. We use these measurements as an opportunity to explore error quantification in measurements of Brownian motion (Catipovic et al. AJP 81(7) 2013). Our advanced lab module is intended to be an introduction to physics research, fortify concepts from optics and statistical physics, and give students hands-on experience in building optical systems and analyzing noisy data.