Elliptically shaped surfaces have the interesting property that light or sound produced at one focus will be reflected to the other focus.
This reflecting property of the ellipse is useful in the design of optical apparatus, and it accounts for the strange "whispering gallery" effect that can be noticed in buildings with elliptical ceilings. In such a building, words whispered softly at one focus can be heard clearly at the other focus.
Among the most famous whispering galleries are the St. PaulĀ“s Cathedral in London, or the National Statuary Hall of the Capitol in Washington, D. C.
Figure 1: St. Paul's Cathedral in London |
Figure 2: Construction sketch |