How do you measure something that travels nearly 300,000 kilometres per second? Students in Dayton Preissl’s Advanced Placement (AP) Physics class recently found out by putting one of science’s most famous numbers—the speed of light—to the test.
Using a laser, a function generator and an oscilloscope, the class set up a hands-on experiment to explore kinematics and the principles of motion. Working in teams, students carefully recorded data, monitored wave signals on the oscilloscope, and adjusted the distance between the light source and a mirror—eventually stretching their setup into a neighbouring classroom—to compare the outgoing and returning signals.
Their goal was to confirm a cornerstone of modern physics: the speed of light is constant, one of Einstein’s key postulates of special relativity.
“Experiments like this help students gain a practical understanding of measurement, precision and teamwork,” said Preissl. “Small details, such as aligning the mirror or securing connections, quickly show how accuracy affects results, while repeated testing builds skills with the same kinds of instruments used by engineers and researchers.”
Beyond the thrill of replicating a famous experiment, students also discovered why this constant matters in everyday life. Technologies such as GPS depend on knowing the speed of light with incredible accuracy—after all, light is so fast it can circle Earth’s equator more than seven times in a single second.
The equipment for this experiment was made possible through the Parents’ Auxiliary, giving students the chance to experience physics not just as theory, but as discovery.
AP Physics Speed of Light Experiment
AP Physics Speed of Light Experiment
AP Physics Speed of Light Experiment
AP Physics Speed of Light Experiment
