Converging lens sim
Slide the lamp along an optical bench; the screen finds the focused image from 1/f = 1/u + 1/v (real-is-positive).
Light: real images · covers the IGCSE, GCSE, O-Level topic
What the sim shows
A thin converging lens (f = 100 mm) on an optical bench. The lamp's 20 mm arrow sits u from the lens; the screen drives to v = uf/(u − f), from the lens equation 1/f = 1/u + 1/v, where the image is sharp. The image is real, inverted and m = v/u times the arrow's size: at u = 2f = 200 mm it is the same size at v = 200 mm, closer in it grows and moves away, and as u falls to the principal focus F (u = f) it runs off to infinity. Inside f there is no real image, only a virtual, upright, magnified image on the same side as the object (a magnifying glass), so the lamp stops at 120 mm. Thin-lens, paraxial model: lens thickness and aberrations are ignored.
- Screen: the real image, inverted
- Lamp box: 20 mm upright arrow cut-out (points up)
- Converging lens, f = 100 mm
Use it in your lessons
- Try it here: anyone can unlock 2 figures free, and a free account unlocks up to 5. Runs on a laptop, a Chromebook or a phone; nothing to install.
- Present it and share student links with the teacher plan, from US$5 a month, billed yearly.
- Put it on your own website or LMS for US$9, paid once, or every sim from US$29 a month.
Free guide: 12 practicals as sims, and how to run one in a lesson →
Need a version for your exact set-up? Have one made: US$49 a figure in an order of 5.
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