Light and Lenses

1. Light and Lenses How is light affected by convex and concave lenses?

2. Lenses Lens- A transparent object with at least one curved surface. All lenses refract light that passes through them.

3. Convex Lens- Thicker in the center than at the edges. Brings light rays together at focal point. • Focal Point- The point at which light rays passing through a lens come together. • When close to an object, convex lens magnifies object. When further, object is upside down. • Concave Lens- Thicker at edges than in center. Causes light rays to spread out. • Image viewed through concave lens smaller and always right side up. Lens Shape

4. Eye and camera both have convex lens. • Both “take pictures”, but cameras take one at a time, and the eye continuously takes them. • Retina-Light sensitive layer at the back of the eye that image is focused on. • It sends message to the brain for interpretation. • Camera focuses by moving lens in and out, with eye muscles in eye cause lens to curve more or less. The Eye and a Camera

5. Near-sighted people have trouble seeing things in distance. • Eyes focus images in front of retina instead of on. • Concave lenses correct near-sightedness • Far-sighted people see objects far away clearly, but have trouble seeing close things clearly. • Convex lenses used to correct far-sightedness Correcting Vision

6. Contact Lenses- clear, thin lenses that are placed on the eye in front of cornea. • Change path of light, but concave lenses used for both types of vision problems. • First lenses hard plastic, now soft and flexible. Contact Lenses