# Proving the Reflection Property of an Ellipse (VIDEO!)

The Mormon Tabernacle in Salt Lake City and the Whispering Gallery in the US Capitol Building are each the shape of an ellipse. This means that if you stood at one focus of the ellipse, each sound wave from a whisper you make will bounce off the wall and head directly to the second focus point. Moreover, all the sound waves will travel the same distance and so arrive in synchronicity at that point. This means a friend standing there will hear and understand your whisper perfectly!

In this video we explain how reflections work and prove mathematically that ellipses do indeed have this astounding property.