This paper demonstrates the use of smartphones in an experiment of light absorption and light scattering. The LED display and camera of the smartphone are used as the light source and as the detector, respectively. The color wheel is used to choose the color of the light source to be shone through the sample for analysis. The detector directly measures the intensity of the light that passes through the sample to study light absorption according to the Beer–Lambert law. On the other hand, to investigate the light scattering, the detector orthogonally measures the intensity of the scattered light from the sample. The results of the light absorption correspond to the Beer–Lambert law. The scattered light from the sample is be measured by a smartphone. The experiment is easy to set up, without the need for any further expensive apparatus. We expect that this experiment will be useful for physics teachers to demonstrate light absorption and light scattering in the classroom or in a physics laboratory.

This paper demonstrates a physics laboratory experiment for determining the coefficient of static friction from circular motion using a smartphone's sensors. The coefficient of static friction between the surface of a smartphone and a turntable can be determined from the limiting value of the static friction that keeps the smartphone in a circular path. The smartphone was used to record an angular speed with an appropriate application (app) to determine the limiting value of angular speed in a circular motion. This limiting value was further calculated to obtain the static friction coefficient. We expect this experiment to be useful for physics teachers to help demonstrate the topic of circular motion.

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This paper describes the use of a smartphone's sensors to investigate the motion of a torsion pendulum to demonstrate energy conservation. The smartphone was placed on and attached to a metal disk hanging by a wire. The oscillation of the disk was measured using the smartphone's sensors to simultaneously record angular position, angular speed and angular acceleration. These experimental data were processed to demonstrate mechanical energy conservation during oscillation. We expect that this smartphone-based experiment will be useful for physics teachers and can make students better understand an oscillating disk's relationship with energy conservation.

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