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# Refraction and lenses

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### Refraction and lenses

1. 1. Refraction and Lenses<br />7SCIENCE<br />
2. 2. Review: What is refraction?<br />Refraction occurs when light bends <br />Light bends as it passes from one substance to another<br />Ex. A straw in a glass into water <br />Refraction can be caused by a lens<br />A lens is a transparent object with at least one curved side that causes light to bend<br />More curved sides = more light bends<br />
3. 3. Lenses<br />Concave and convex lenses form images OPPOSITE to that in concave and convex mirrors<br />Convex lens<br />Thicker in the center than at the edgesex: magnifying glass<br />Concave lens<br />Thicker at the sides that in the center<br /> ex: glasses for people that cannot see far objects<br />
4. 4. Convex lenses<br />Light rays travelling through a convex lens are bent so they meet at a focal point<br />Image formed is similar to that of a concave mirror<br />If the object is 2+ (or more) focal lengths from the lens, the image appears inverted and smaller<br />If the object is closer to the lens than one focal length, the image is upright and larger<br />
5. 5. Concave lenses<br />Light rays travelling through a concave lens are bent and spread away from each other, do not meet <br />Image formed is similar to thatof a convex mirror<br />Image formed is upright and smaller than the object<br />Ex: eyeglasses if you cannot see far<br />
6. 6. Which pictures show a concave lens? Convex lens? How do you know?<br />