A myth of Archimedes in the 3rd c. BCE was using the sun to burn attacking ships. Leonardo also wanted to use the power of the sun. He studied light to show the cylindrical mirrors in use diffused sunlight and were not efficient for heating. (below left.) He realized the need for a parabolic mirror to concentrate sun to a single focus. (below right.)
Leonardo designed a parabolic compass to help create such mirrors (left) and Chuck built this parabolic compass based on that design (right).
Chuck’s parabolic compass was used to mark cardboard pieces which were glued together to make a burning mirror (below). Notice the caustic formed by the parabolic trough. Light from the sun is reflected to a single concentrated point.
The same principle is the basis for solar ovens and heat collectors. It applies to the entire electromagnetic field (radio, TV, microwaves, gamma rays, etc.)
Conics or Shapes Created by a Plane Intersecting a Cone
A parabola in the physical world is formed by the intersection of a cone with a plane. A parabola is formed if the plane is parallel to the cone. (left) Other shapes may also be created including a circle (plane perpendicular to axis of cone), ellipse, and hyperbola. (below right)
Ink Brush Painting 