Download - Refraction and lenses
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Refraction and Lenses7SCIENCE
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Review: What is refraction?• Refraction occurs when light bends – Light bends as it passes from one
substance to another– Ex. A straw in a glass into water
• Refraction can be caused by a lens• A lens is a transparent object with at least one
curved side that causes light to bend– More curved sides = more light bends
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Lenses• Concave and convex lenses
form images OPPOSITE to that in concave and convex mirrors
• Convex lens– Thicker in the center than at
the edgesex: magnifying glass
• Concave lens– Thicker at the sides that in the
center ex: glasses for people that cannot
see far objects
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Convex lenses
• Light rays travelling through a convex lens are bent so they meet at a focal point
• Image formed is similar to that of a concave mirror– If the object is 2+ (or more) focal lengths from the
lens, the image appears inverted and smaller
– If the object is closer to the lens than one focal length, the image is upright and larger
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Concave lenses
• Light 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 mirror– Image formed is
upright and smaller than the object
– Ex: eyeglasses if you cannot see far
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Which pictures show a concave lens? Convex lens? How do you know?