Interactive explorer

Explore: the thin-lens model

Change the lens and object, predict the signs of the image quantities, then use the ray diagram to check your reasoning.

Schematic geometry: axial and transverse scales intentionally differ to keep the rays legible; the calculated values at right are exact for the ideal thin-lens model.

Try it

Move the object toward the lens. Before it crosses the upstream focal point, predict what will happen to zi and M.