Isabel Salinas

Direct Visualization of Mechanical Beats by Means of an Oscillating Smartphone

The resonance phenomenon is widely known in physics courses. Qualitatively speaking, resonance takes place in a driven oscillating system whenever the frequency approaches the natural frequency, resulting in maximal oscillatory amplitude. Very closely related to resonance is the phenomenon of mechanical beating, which occurs when the driving and natural frequencies of the system are slightly different. The frequency of the beat is just the difference of the natural and driving frequencies. Beats are very familiar in acoustic systems. There are several works in this journal on visualizing the beats in acoustic systems. For instance, the microphone and the speaker of two mobile devices were used in previous work to analyze the acoustic beats produced by two signals of close frequencies. The formation of beats can also be visualized in mechanical systems, such as a mass-spring system or a double-driven string. Here, the mechanical beats in a smartphone-spring system are directly visualized in a simple way. T...

Characterization of linear light sources with the smartphone’s ambient light sensor

The smartphone’s ambient light sensor has been used in the literature to study different physical phenomena. For instance, Malus’s law, which involves the polarized light, has been verified by using simultaneously the orientation and light sensors of a smartphone. The illuminance of point light sources has been characterized also using the light sensor of smartphones and tablets, demonstrating in this way the well-known inverse-square law of distance. Moreover, these kinds of illuminance measurements with the ambient light sensor have allowed the determination of the luminous efficiency of different quasi-point optical sources (incandescent and halogen lamps) as a function of the electric power supplied. Regarding mechanical systems, the inverse-square law of distance has also been used to investigate the speed and acceleration of a moving light source on an inclined plane or to study coupled and damped oscillations. In the present work, we go further in presenting a simple laboratory experiment using the smartphone’s ambient light sensor in order to characterize a non-point light source, a linear fluorescent tube in our case.The smartphone’s ambient light sensor has been used in the literature to study different physical phenomena. For instance, Malus’s law, which involves the polarized light, has been verified by using simultaneously the orientation and light sensors of a smartphone. The illuminance of point light sources has been characterized also using the light sensor of smartphones and tablets, demonstrating in this way the well-known inverse-square law of distance. Moreover, these kinds of illuminance measurements with the ambient light sensor have allowed the determination of the luminous efficiency of different quasi-point optical sources (incandescent and halogen lamps) as a function of the electric power supplied. Regarding mechanical systems, the inverse-square law of distance has also been used to investigate the speed and acceleration of a moving light source on an inclined plane or to study coupled and damped oscillations. In the present work, we go further in presenting a simple laboratory experiment using the...