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• Refraction is the change in direction of a wave due to a change in its speed. This is most commonly observed when a wave passes from 1 medium to another at an angle. http://www.stmary.ws/highschool/physics /home/notes/waves/refraction/fishRefract ion.html Straight or bent? What happens when you look at the pencil through the side of the glass? Light play tricks on your eyes. The pencil looks bent. This is because light travels slower through water than through air. As the light enters the glass of water it slows down(changes direction) and as it leaves the glass it speeds up again – therefore making the pencil look as though it is bent A lens is a piece of transparent material. It is usually made of glass and has at least one curved surface. The curved surface/surfaces of a lens bends the light. The angle of incidence is measured from the normal to the incident ray. The angle of refraction is measured from the normal to the refracted ray. • • If light enters a more optically dense material, the speed decreases and the light bends towards the normal. If light enters a less optically dense material, the speed increases and the light bends away from the normal. Did you know.... A sunset is an optical illusion Refraction allows you to see the sun even after it has set. Reflection Reflection •Reflection- the return of light, heat, sound, etc., after striking a surface. •bouncing of light off a mirror or mirror-like surface. Diffuse Reflection – reflection off an irregular surface causing light to scatter (no image) Regular Reflection reflection off a polished surface (produces images) Polarized light vibrates on only 1 plane Polarizing filters are used in photography and some sunglasses Cornea: transparent covering of the front of the eye. ◦Allows for the passage of light into the eye and functions as a fixed lens. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings The iris regulates the size of the pupil. Retina: lines the interior surface of the eye ◦Contains photoreceptors. Except where the optic nerve attaches Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Mammals focus light by changing the shape of the lens. The lens is flattened for distant objects. The lens is rounded for near objects. Photoreceptors of the retina ◦rod cells - light sensitive but do not distinguish colors. ◦cone cells - not as light sensitive as rods but provide color vision Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings