L3-19. Penny And Parabolic Mirrors

Purpose

Classic illusion of penny levitating above a pair of parabolic concave mirrors.

Equipment

Penny and parabolic mirror illusion.

Images

Description

This commercial apparatus forms a real image of a penny glued to the bottom mirror. Two concave parabolic mirrors with the correct focal length and spacing create an image of the penny levitating on the opening of the upper mirror. The illusion can be viewed within a limited angle, so it is most effective for individual observation. A ray drawing is included which shows how the image is produced.

References

Lecture Demonstrations Ray Diagram for Parabolic Mirrors. ◙Catalog Description, Opti-Thermal Imager. ◙Supplementary Information on Illusion Device, "Reality or Illusion?" ◙Pamphlet, "Mirage" Demonstration. ◙Andrzej Sieradzan, Teaching Geometrical Optics with the "Optic Mirage," TPT 28, 534-536 (1990).