Kinds of lens
Lenses are named by the shape of their two surfaces.
Bi-convex
Plano-convex
Bi-concave
Plano-concave
After Figure 5.32.
| Lens | Its two surfaces |
|---|---|
| Bi-convex | Both convex |
| Plano-convex | One convex, one flat |
| Bi-concave | Both concave |
| Plano-concave | One concave, one flat |
Convex lenses
Thicker in the middle than at the edges. They bring parallel light together.
Concave lenses
Thinner in the middle than at the edges. They spread parallel light apart.