Ray diagram
The canvas plots the optical axis, focal points, object arrow, image arrow, and the three principal rays. Virtual rays are dashed for easy differentiation.
FAQ
How do I know if the image is real or virtual?
The sign convention follows the Gaussian Cartesian rule: dᵢ > 0 indicates a real image on the outgoing side, whereas dᵢ < 0 marks a virtual image on the object side. The magnification sign shows whether the image is upright (m > 0) or inverted (m < 0).
What ray diagram does the tool draw?
We plot the parallel ray through the focus, the ray that heads toward the focus and exits parallel, and the central ray. Dashed segments denote virtual extensions so diverging lenses and convex mirrors remain easy to follow.
Related calculators
How it's calculated
- Thin lens: 1/f = 1/do + 1/di with sign conventions.
- Computes magnification and image orientation.
- Share URL preserves inputs and units.