Application of the Lambert-Beer legal concept in learning spectroscopy UV-Vis with simple spectrophotometers

Education 4.0 encourages the development of learning that integrates technology in it. Thereby, it is important to guide students to be more creative and innovative. Electronic devices are quite expensive for students in the SMA / SMK level, so to teach the concepts and practice of Lambert-Beer law is very difficult. Therefore, an alternative is needed in teaching the concept of spectroscopy by making a simple spectrophotometer. The spectrophotometer is made to detect solutions in the visible area, then the data are analyzed by capturing light from the samples using a smartphone camera and using an application on the Google Play Store. The application can be used to determine the absorbance value of a solution, so a calibration curve can be made between absorbance vs. concentration. This study uses an experimental method with a product that uses a spectrophotometer where the instrument has been tested for eligibility based on previous research, then the reading data using the Google Play Store application is validated with a Spectro UV-Vis (with some specifications such as the source of light, the monochromator, diffraction grating, and direct reading system). It is used to measure the concentration of a standard solution of the Fe (II) -phenanthroline complex at pH 4.0 in an acetate buffer solution and a wavelength of 510 nm. The results of concentration measurements using the standard solution with a spectrophotometer UV-Vis and a simple spectrophotometer successively give the value R² = 0.9985 and R² = 0.9983. Based on the results obtained, it can be concluded that the simple made of spectrophotometer can be used for learning Lambert-Beer Law because it gives results that are significantly the same as any standard of a spectrophotometer.