Lenses
OBJECTIVE CONTRAST WAYS IN WHICH LIGHT RAYS ARE BENT BY CONCAVE AND CONVEX LENSES [COS 5 SAT 10]
LENSES DEFINITION: Part of the eye that can focus light A piece of clear glass or plastic that bends light rays passing through it Part of the eye that can focus light The lens is found behind the pupil. It bends light that enters the eye.
LENSES THERE ARE 2 TYPES OF LENSES: 1. Convex Lenses Concave Lenses
CONVEX LENS A convex lens is thicker in the middle than at the edges. When light passes through a convex lens, the rays bend toward each other. It makes nearby objects look bigger. Have everyone look through a magnifying glass to verify that things already close look bigger. Can also look through a 2 liter bottle or clear jar with water inside to magnify.
CONVEX LENS People sometimes need lenses to help them see better. What are people called who need convex lenses? Farsighted – these people have trouble seeing up close. They wear glasses or contacts that are thicker in the middle than at the edges. Glasses or contacts with convex lenses magnify the print, allowing these people to read more easily.
CONVEX LENS Besides glasses and contacts, can you name other convex lenses? MOVIE PROJECTOR Did you know that the light rays bent by a convex lens all meet at one point then cross, making the image on the screen appear upside down. So slides or movie film must be put into the projector upside down. For the telescope, you can hold 2 magnifying glasses in each hand and look through them to create a telescope. Binoculars are like 2 telescopes stuck together, so each eye has its own telescope. SLIDE PROJECTOR TELESCOPES BINOCULARS
LENSES THE SECOND TYPE OF LENS IS KNOWN AS A CONCAVE LENS.
CONCAVE LENSES The lens is thicker around the edges than in the middle When light rays pass through a concave lens, they bend away from each other. This makes distant objects seem nearer and smaller. Exp: camera viewfinder
CONCAVE LENSES Concave lenses help people who are nearsighted. These people have trouble seeing distant objects. Concave lenses bend light rays outward just enough to make distant obj. seem closer. A dentist uses concave lenses
CONTRAST LENSES CONCAVE LENSES CONVEX LENSES Thicker around the edges than in the middle Help nearsighted people When light rays pass through a concave lens, they bend away from each other. CONVEX LENSES Thicker in the middle than at the edges Help farsighted people When light passes through a convex lens, the rays bend toward each other.
Advantages of Lenses Lenses allow high magnification when they are used in microscopes or telescopes. They are also used in cameras and powerful spotlights Lenses have opened a whole new world to scientists Lenses can lead you out beyond the Earth, to the farthest reaches of the galaxy
OBJECTIVE CONTRAST WAYS IN WHICH LIGHT RAYS ARE BENT BY CONCAVE AND CONVEX LENSES
CONTRAST LENSES CONCAVE LENSES CONVEX LENSES Thicker around the edges than in the middle Help nearsighted people When light rays pass through a concave lens, they bend away from each other. CONVEX LENSES Thicker in the middle than at the edges Help farsighted people When light passes through a convex lens, the rays bend toward each other.
LENS WRAP UP QUESTIONS SUGGESTIONS ON MAKING THE PRESENTATION MORE EFFECTIVE