Abstract: In this paper, three smart phones and a self-made cassette are used to perform an optical determination of the relative time of paper production. Based on different cellulose content in the same paper of different ages, the glucose concentration of the solution is different after hydrolysis, which in turn leads to different ways of acting on light (absorbance) after color development. The color of the sample hydroxylation is processed and a new double-layer glass slide model is adopted, which made up for the shortcomings of traditional experiments in offsetting the reflected light. Three smart phones are used as the light source end, the detection end and the control end, respectively. Among them, the detection end is based on the Phyphox software to detect the changes of the incident light intensity and the transmitted light intensity with time, and processes the data through the Lambert-Beer law to obtain the functional relationship between the absorbance and the age of the paper. Taking the People's Daily on January 10, 2017 as the paper to be tested, the detected value is 2017.163. Comparing the detected value with the real value proves the reliability of the Lambert-Beer law and the feasibility of the self-made experimental device.

Key words: phyphox, relative time of paper formation, double-layer slide model, Lambert-Beer law, absorbance