PURPOSE: To demonstrate construction of a Fresnel lens.

DESCRIPTION: Set up the hyperbolic convex lens with the seven-ray slit baffle so that the entire aperture of the lens is used (left). Then replace the regular lens with the hyperbolic Fresnel lens, on which one of the light rays uses each separate segment in the lens (right). This shows how to construct a lens which focuses like a standard double convex lens but uses much less material.

SUGGESTIONS: A slide is available illustrating how this lens was actually constructed. See Question of the Week #312 for information on using this demonstration to enhance class involvement.

REFERENCES: (PIRA 6A65.70) See Demonstration Reference File for information on Fresnel lenses as well as construction details for our large Fresnel lens.

EQUIPMENT: Optical board with 18 inch hyperbolic and Fresnel lenses. Optical Board Configuration

SETUP TIME: None.