We all know that a light, such as a candle or a streetlight, looks dimmer the farther away from it we get. This classroom activity gives an easy way for students to measure the relationship between distance and brightness. Once students discover the relationship, they can begin to understand how astronomers use this knowledge to determine the distances to stars and far away galaxies.
http://wise.ssl.berkeley.edu/documents/The%20Inverse%20Square%20Law%20of%20Light_Final.pdf
