Eyes and Vision 2 - Focusing Light

Have you ever used the lens of a magnifying glass to focus sunlight to a point? This only works if you get the distance between the lens and the ground just right. This distance depends on two things: the shape of the lens and the distance to the light source—which in this case is very far!

The lenses in your eyes work the same way to focus light on the retina. Since the distance between the lens and retina is constant, the shape of the lens must change to keep the light focused as the distance to the object changes. Your lenses are constantly making small changes in shape to adjust to what you are looking at.

Students can use the Eyes and Vision 2 – Focusing Light Gizmo to explore how the lens forms a focused image on the retina. Students can manipulate the object distance and light intensity, then adjust the lens shape and pupil diameter to create the image. The Gizmo shows both the side view of the object and a view of exactly what the eye is perceiving, showing the resulting blur and brightness of the object. Using this Gizmo, along with Eyes and Vision 1 and 3 Gizmos, will help students form a clear picture about how we see.