Abstract: Based on the principle of geometric optics, a platform for measuring the refractive index of liquid was built by means of spectrometer, helium-neon laser and self-designed constant deflection prism glassware. With the assistance of real-time sensing function of smart phone light sensor, the deflection angle of the optical path in the constant deflection prism was easily and quickly determined to obtain the refractive index of liquid. The refractive index of deionized water and NaCl solution with different concentrations is determined accurately in this method, and the refractive index measurement error is much lower than 5%. The constant deflection prism optical path has the advantages of ingenious design, simple angle judgment, convenient operation, obvious experimental phenomenon, accurate and reliable measurement results, and scientific and feasible design method. It can be popularized as a new method for measuring the refractive index of liquid and as a new comprehensive design of university physics experiment project.

Key words: spectrometer, refractive index, constant deflection prism, smart phone sensor