Explore image formation on a movable optical bench. Focus a screen, compare converging and diverging lenses, draw your own principal rays and use original exam-style investigations to connect observations with explanations. The lab opens without an account.
What you can investigate
- Movable objects, lenses, mirrors, screens and ruler cursors
- Converging and diverging lenses; real and virtual images
- Draw-your-own principal rays with individual construction feedback
- Screen focus, geometrical blur, image size and magnification
- Ten guided investigations with original exam-style questions and mark schemes
- Concave and convex mirror extensions
- Captured measurements, CSV tables, SVG diagrams and saved experiments
How does object distance change the image?
- Start with Find a sharp image. Drag the screen until its image is sharp, then capture a reading.
- Move the object nearer the lens while keeping it outside the focal length. Refocus the screen and compare the screen distance and image size.
- Choose Construct a ray diagram. Draw a parallel ray and a centre ray, check their paths, then place the image tip at their intersection.
A converging lens forms a real, inverted image when the real object lies beyond its focal length. As the object approaches F from outside, the image moves further away and grows. Inside F, the image is virtual, upright and magnified: backward extensions meet, but the outgoing light does not meet at the virtual image.
Interpreting the model
One ideal thin lens or paraxial mirror in air. Aperture clips rays; aberrations and diffraction are excluded. Screen focus is based on geometrical ray spread, with a 3 mm sharpness threshold. Screen distance is recorded as an image measurement only at focus. Lens-equation calculations and curved mirrors are labelled extensions. Animated markers illustrate ray construction at a slowed display speed.
Revision and practice