Visualizing the Beat Phenomenon Between Two Amplitude-Modulated Light Beams on a Solar Cell Using Smartphones

[EN] The beat phenomenon arises when two harmonic oscillations of slightly different frequencies (f1 and f2) are superimposed. This phenomenon has been extensively exemplified in physics teaching journals for different contexts. For instance, the acoustic beats between sound waves have been studied with tuning forks, conventional speakers3 and microphones, and, more recently, smartphones. Likewise, the mechanical beat has been studied using a spring-mass system or a pendulum. The beat can also be visualized on the oscilloscope screen by superimposing electrical signals. In relation to light waves, there are also reported works in the literature. More exotic cases are, for instance, the ¿beating¿ phenomenon in the oscillation of the synodic period of the Moon or the beats displayed with foam packing.