Xavier Bacalla, Edcel John Salumbides
We demonstrate that the time profile of the light intensity from domestic lighting sources exhibits simple yet interesting properties that foster lively student discussions. We monitor the light intensity of an industrial fluorescent lamp (also known as TL) and an incandescent bulb using a photodetector connected to an oscilloscope. The light intensity of these sources displays modulation at twice the ac power supply frequency. The familiarity of ac line power supply, commonplace light sources, and simplicity of the setup encourage student confidence, allowing them to think deeper and continually reassess their notions, and if managed can lead to a satisfactory explanation of the observations. © 2013 American Association of Physics Teachers.
Department of Physics, University of San Carlos, Cebu City, Cebu, 6000, Philippines; Department of Physics and Astronomy and LaserLaB, VU University, De Boelelaan 1081, Amsterdam, 1081 HV, Netherlands
