Introduces the method of ray tracing to analyze the refraction or reflection of real or virtual images from multiple optical devices. Discusses ray-tracing techniques for locating images using convex and concave lenses or mirrors. (MDH)

Introduces a new sign convention for the object and image distances involving mirrors and lenses. Proposes that the method is easier for students to understand and remember and that it helps clarify the physics concepts involved. (MDH)