Thin Lens (Image Formation)
Place an object in front of a converging or diverging lens — watch the three principal rays trace out where the image forms, and see whether it's real or virtual, upright or inverted, magnified or reduced.
Preview — sign up free to change the numbers yourself
What you can adjust
- Lens type
- 0 – 1
- Focal length (magnitude)
- 0.2 – 3 m
- Object distance
- 0.3 – 6 m
- Object height
- 0.1 – 2 m
Converging (convex) lenses bend light inward and can form real or virtual images. Diverging (concave) lenses always spread light apart and only ever form virtual, upright, reduced images.
How strongly the lens bends light — a shorter focal length bends light more sharply.
How far the object sits in front of the lens. For a converging lens, moving this inside the focal length (magnifying-glass territory) flips the image from real+inverted to virtual+upright+magnified.
How tall the object arrow is — doesn't change the image distance or magnification, just how big everything looks.
About this simulation
What it shows
An object stands in front of a lens, and the three standard rays are traced to show where the image forms. The readout says whether the image is real or virtual, upright or inverted, and larger or smaller.
The key idea
A lens obeys 1/f = 1/d_object + 1/d_image. A converging lens makes a real, inverted image when the object is beyond the focal length and a virtual, upright, magnified one when it is inside it. A diverging lens always gives a smaller virtual image.
Try this
With the converging lens, move Object distance from 3 m to 0.5 m, inside the 1 m focal length: the image flips from real and inverted to virtual, upright and magnified.
This is an ideal thin lens: all rays meet at a single point, with none of the blurring or colour fringes of real glass.