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Convex Lens Imaging

About this simulation

Convex Lens Imaging uses a thin-lens model with distances in centimeters. Students change the object distance and the focal length, and can show dashed virtual extensions of the rays. Readouts give the image distance, magnification, image height and image type. It lets learners practice ray diagrams, see why the image flips when the object is beyond the focal length, and discover the magnifying glass case when the object sits inside the focal length.

What students can explore

  • Move the object beyond twice the focal length and note the image size and type.
  • Place the object exactly at the focal length and watch the rays become parallel.
  • Move the object inside the focal length and turn Show virtual extensions on.
  • Increase Focal length and see how Image distance di changes.
  • Check that the Magnification sign matches an inverted or upright image.

Learning objectives

  1. 1Use the thin-lens equation to find an image distance.
  2. 2Draw and interpret the three principal rays.
  3. 3Distinguish real from virtual images.
  4. 4Relate object distance to magnification and orientation.

Questions teachers ask

Is the Convex Lens simulation free?

Yes. It is free, requires no sign-up and runs in any modern browser, including classroom whiteboards and tablets.

When is the image virtual?

When the object is closer to the lens than the focal length. The rays spread apart after the lens, so you see an upright, magnified image on the object side, as with a magnifying glass.

How do I use it?

Set the object distance and the focal length, then follow the three rays to the image tip. Read the image distance, magnification and image type, and turn on virtual extensions when needed.

What does a negative magnification mean?

It means the image is inverted compared with the object. Magnification is minus the image distance over the object distance, so a positive value is an upright image.

Embed this simulation

Drop it into your LMS, blog, or class site — free.

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