PURPOSE: To use principal rays to locate a virtual image produced by a convex lens.
DESCRIPTION: The central ray passing through a half-silvered mirror serves as the optic axis, and the vertical ray between the two mirrors serves as the object arrow. By rotating the mirror at the tip of the arrow the three principal rays (or other rays) can be produced, all of which appear to be emanating from the image point. The focal points of the lens, about 17" (43cm) from the lens surface, can be indicated using squares of masking tape or black tape. A single converging lens in front of the object is used to keep the ray narrow. The object should be about 30cm from the surface of the lens. The image position is found by tracing the principal rays back behind the object with a meterstick or by rotating the object mirror while watchin g where the rays cross.
REFERENCES: (PIRA unknown.)
EQUIPMENT: Optical board with double mirror "object" and hyperbolic lens, spherical lens to keep ray narrow.
SETUP TIME: None.
Go back to Lecture-Demonstration Home Page.