Remotely Teaching Optics with Smartphone Camera

The COVID-19 pandemic forced many in-person events to be held remotely, and these events often had to be redesigned or modified to compensate. In physics classrooms, instructors replaced many experiments requiring specialized equipment with alternative activities that could be performed at home while still conveying the necessary information.

Sullivan detailed one such alternative experiment, where students could study the thin lens equation using a smartphone camera to teach principles in optics.

“The camera lens obeys the thin lens equation quite well — except when it does not!” said author Matthew C. Sullivan. “This experiment explores why the camera lens acts so much like a single thin lens and explains why and when it doesn’t act like a single lens.”

Using a ruler and open-source image software, students can calculate the effective focal length of their phone’s camera as if it were a single thin lens and, under most circumstances, are able to get reasonable answers. However, the simple linear relationship in the thin lens equation between object distance and image height fails when students try to use the model to explain the intercept of the linear fit in addition to the slope.

Sullivan emphasizes this experiment has something to offer for students at multiple education levels.

“The experiment can be quite simple with data analysis that is consistent with the theories we learn in introductory courses, but it can also be expanded for more advanced students,” said Sullivan. “These students can look for and try and understand when and why the models we use in introductory physics fail.”

Source: “Using a smartphone camera to explore ray optics beyond the thin lens equation,” by M. C. Sullivan, American Journal of Physics (2022). The article can be accessed at https://doi.org/10.1119/5.0090854 .