The idea to use smartphone for measuring the light intensity passing trough 2 polarizers as cos² of the angle between their axes (Malus’ law) is not new. See, for example, Martín Monteiro, Cecilia Stari, Cecilia Cabeza, and Arturo C. Martí, "The Polarization of Light and Malus’ Law Using Smartphones," The Physics Teacher 55, 264 (2017); doi: 10.1119/1.4981030 . But not all telephones have a light sensor 
. So, here is an experiment using the SensorTag of Texas Instruments controlled by a smartphone via Bluetooth. The corresponding phyphox program is attached here. The angle of rotation is determined from x and y components given by the SensorTag acceleration sensor. It is much easier to rotate the SensorTag than a smartphone. One polarizer film is in front of the light source and another is attached to the SensorTag.
There is a little problem of synchronization of two sensors
. It is not sufficient to use the same interval of measurements (0.8 s)...
. So, here is an experiment using the SensorTag of Texas Instruments controlled by a smartphone via Bluetooth. The corresponding phyphox program is attached here. The angle of rotation is determined from x and y components given by the SensorTag acceleration sensor. It is much easier to rotate the SensorTag than a smartphone. One polarizer film is in front of the light source and another is attached to the SensorTag.There is a little problem of synchronization of two sensors
. It is not sufficient to use the same interval of measurements (0.8 s)...