Introduction
You have been working in the lighthouse construction business for several years now, and have found that lugging those huge glass lenses up 100 feet of stairs isn't exactly your idea of fun. There's gotta be a way to make these lenses lighter or smaller, you think to yourself, ascending the narrow lighthouse stairway with a huge hunk of curved glass on your back. How could I make this lens lighter? Is all this glass necessary? How and where does the light bend when it encounters the lens? Your task: determine if this "new-fangled" lens in your Optics Kit will behave the same as a regular lens.Procedure
- Gather these items from your Optics Kit:
- a Fresnel lens (the flat, ridged lens)
- Lenses A and B
- Compare the Fresnel lens to Lens A and B. How is a Fresnel lens similar to a "regular" lens? How is it different?
- Feel the surface of the Fresnel lens. What do you notice? Make a sketch in your notebook of how you think the surface might look up close.
- See the previous Activity, Lenses, and follow the instructions for measuring the focal length and magnification of your Fresnel lens.
- How does the magnification of the Fresnel lens compare to that of the other lenses? Is its focal length shorter or longer than the other lenses?
- Can you find a practical use of a Fresnel lens in cars, flashlights, camping lanterns...?
To read more about Fresnel lenses, go to the Fresnel Lens Readings
Page authored by ACEPT W3 Group
Department of Physics and Astronomy, Arizona State University, Tempe, AZ 85287-1504
Copyright © 1995-2000 Arizona Board of Regents. All rights reserved.
Last modified 15 December 1999
Send Questions or Comments to our webmaster
URL: http://acept.asu.edu/PiN/act/fresnel/fresnel.shtml
Activities