Interest in smartphone-based learning, especially in the use of internal sensors in smartphones for physics experiments, is increasing rapidly. Internal sensors in smartphones such as acoustic sensor, optical sensor, and acceleration sensor can help researchers alleviate the problems including insufficient accuracy with low-cost equipment, high cost of sophisticated experimental equipment, and cumbersome operation of measuring software. In teaching experimental physics, researchers and educators have introduced various internal sensors in smartphones for physics experiments in different fields including acoustics, optics, mechanics, thermology, and magnetics. In this paper, the light sensor in a smartphone is used to measure the period of the oscillation of a simple pendulum. For the experimental equipment, a laser emitter and a smartphone with an internal light sensor constitute a transmitting and receiving system. We use this system to explore expanded pendulum experiments of large pendulum angle, different pendulum lengths, and damping effect.

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