Finding the water refractive index in a swimming pool using a ruler

Abstract When a swimming pool is filled with water, the tiles covering its walls appear to have smaller vertical dimensions than the real ones, due to the refraction of light from the water into the air. This condition was used to find the refractive index of water, using a trigonometric equation developed from a geometrical model. The necessary measurements were made with a common ruler and the average value obtained for the refractive index was very close to the real one, favoring the didactic potential of this experimental activity.