  In this paper we show how to obtain the Inverse-square law of the distance to
the light intensity emitted from a small source in a simple, fast and with good
precision way. With the aid of two smartphones, free apps and a ruler, one is
able to measure the distances between the devices listed (one as a source and
the other as a measuring light intensity) and the respective light intensities
measured by the probeware in the device. The ease of reproduction of the
proposed experiment and the penetration of the use of tablets and smartphones
among students and teachers, could make the proposed activity a good
alternative to the introduction of physical phenomena which exhibit the same
functional dependence, such as the Law of Newton's Universal Gravitation and
Coulomb's Law.
