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Fermat's Principle: Refraction

Authors: Ms. Giselle dos Santos Castro - Federal University of Ceara - UFC
Dr. Nildo Loiola Dias - Federal University of Ceara - UFC

CONTROLS:

- Choose medium 1 (top) out of 5 possibilities.
- Choose medium 2 (bottom) out of 5 possibilities.
- Drag point A to any position.
- Drag point B to any position.
- Drag point P on the separation line between the two media in order to obtain a minimum travel time. The buttons (<<) and (>>) allow a fine control of the position of point P.
- Click the SHOW NORMAL button to draw the normal to the surface at point P.
- Click on the PROTRACTOR button to get a protractor that can be moved to the desired position.
- Click on the SHOW EXTENSIONS button to view the extensions of the incident and refracted rays.

DESCRIPTION OF THE SIMULATION:

This simulation allows you to verify that, according to Fermat's Principle, the path taken by light in the refraction between two points located in different media will be the one for which the travel time is minimal. For this, it is possible to choose the material of each medium, position point A in any position in the medium 1 and the point B in the medium 2 and locate a point P at the interface of the two media in order to minimize the light travel time. By locating the position of point P, which minimizes the travel time, it is possible to measure the angles of incidence and refraction with a protractor and verify that they are in accordance with Snell's law of refraction.

For an analysis of the data, consult one of the proposed ACTIVITY GUIDE.

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