Whispering Gallery

Standing at one end of an elliptical room, you suddenly hear your mother, who is standing at the other end of the room, whispering a secret about you to your friend. You move towards them to better hear the conversation, but as you move the sound fades. You can no longer hear them, even though you are closer than before. How is this possible?

Your mind is not playing tricks on you. What you are witnessing is the reflective properties of conic sections. Remember, you are standing in a room shaped like an ellipse. If light or sound waves are emitted from one focus of an ellipse, they must be reflected to the other focus. You can now turn this to your advantage by whispering, "I can hear you!" from your end of the room.

There is a famous whispering gallery along the base of the dome of St. Paul's Cathedral in London, built by Christopher Wren. The Capitol building in Washington, D.C., also contains a room called Statuary Hall that has a parabolic reflecting ceiling. John Quincy Adams' desk happened to be situated at the focal point of the ceiling, and he discovered that he could overhear conversations from different points around the room.

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