Refraction occurs when light bends as it passes from one substance to another. Lenses cause light to bend based on their shape - convex lenses are thicker in the center and bend light inward to focus it, while concave lenses are thicker on the sides and bend light outward. Convex lenses form inverted and magnified images when the object is beyond the focal point, and upright images when the object is closer. Concave lenses always form upright and smaller images that do not focus due to the light rays spreading out.

1. Refraction and Lenses7SCIENCE

2. Review: What is refraction?Refraction occurs when light bends Light bends as it passes from one substance to anotherEx. A straw in a glass into water Refraction can be caused by a lensA lens is a transparent object with at least one curved side that causes light to bendMore curved sides = more light bends

3. LensesConcave and convex lenses form images OPPOSITE to that in concave and convex mirrorsConvex lensThicker in the center than at the edgesex: magnifying glassConcave lensThicker at the sides that in the center ex: glasses for people that cannot see far objects

4. Convex lensesLight rays travelling through a convex lens are bent so they meet at a focal pointImage formed is similar to that of a concave mirrorIf the object is 2+ (or more) focal lengths from the lens, the image appears inverted and smallerIf the object is closer to the lens than one focal length, the image is upright and larger

5. Concave lensesLight rays travelling through a concave lens are bent and spread away from each other, do not meet Image formed is similar to thatof a convex mirrorImage formed is upright and smaller than the objectEx: eyeglasses if you cannot see far

6. Which pictures show a concave lens? Convex lens? How do you know?