🧭 Plot Summary
A lens is a piece of clear material with curved surfaces, and every curved surface bends light by refraction. Shape it so the glass is thicker in the middle and parallel rays all bend toward a single point. That’s a converginglens, the kind in a magnifying glass, a camera, and your own eye. Shape it thinner in the middle and the rays spread out. That’s a diverging lens.
You’ll find a lens’s focal length by focusing a distant window onto a card, then use the same lens to make real images at different distances and test the lens equation against your own measurements. Then you’ll see how a lens placed in front of an eye can pull a blurry image back into focus, which is the answer to how glasses work.
What you will do in this activity
- Focus a distant window onto a card to find a lens’s focal length.
- Form real images on a screen at different object distances, and test the lens equation against your own data.
- Find out why a magnifying glass only magnifies when the object is close, and why a diverging lens never makes an image you can catch.
- Convert focal lengths to the diopters on an eyeglass prescription.
- Explain how a lens in front of your eye moves a blurry image back onto the retina.
Why it matters
This is the last of the three tricks light can do, and the one you’ll use the most. Lenses are the parts of the optical device you’ll build in Project 6-1-4, and the whole of the vision aid you’ll design in Problem 6-2-1.
✅ Self-Check Before You Roll On
Check off each item as you get there. These are not grades — they are your own signal.