(c) McGraw Hill Ryerson 2007

5.3 Using Lenses to Form Images

• A lens is a piece of transparent material that can bend, or refract, light rays in useful ways to help form a well-focused image.

• A lens can be concave or convex.

See page 190

(c) McGraw Hill Ryerson 2007

Concave Lenses

• Concave lenses are thinner in the middle than at the edge.

• Concave lenses cause light rays to diverge.• Concave lenses produce images that are upright and smaller than the object.

• Concave lenses are sometimes used in eyeglasses and telescopes.

See page 191

Concave Lenses

(c) McGraw Hill Ryerson 2007

(c) McGraw Hill Ryerson 2007

Convex Lenses

• Convex lenses are thicker in the middle than at the edge.

• Convex lenses cause light rays to converge. When parallel rays strike a convex lens they come together at the focal point.

• A magnifying glass is a good example of a convex lens.

See page 192

(c) McGraw Hill Ryerson 2007

Focal length in Convex Lenses

The distance from the centre of the lens to the focal point is called the focal length.

The type of image a convex lens forms depends on where the object is relative to the focal point.

Focal Length in Convex Lenses

(c) McGraw Hill Ryerson 2007

Focal Length in Convex Lenses

(c) McGraw Hill Ryerson 2007

Focal Length in Convex Lenses

(c) McGraw Hill Ryerson 2007

Focal Length in Convex Lenses

(c) McGraw Hill Ryerson 2007

Take the Section 5.3 Quiz