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Chapter 5-3 Using Lenses to Form Images

Page history last edited by PBworks 12 years, 6 months ago

 A lens is a piece of transparent material that can bend or refract, light rays in useful ways to help form a well-focused image. Such lense are concave lense and convex lenses.

 

         Concave lenses - are lenses that are thinner in the middle and thicker at the edge. The light rays that pass through a concave lens diverge will be refracted outward.

                                           The rays will never meet at a focal point. The images always appear upright and smaller than the actual object. USED IN: EYEGLASSES AND SOME TELESCOPES.

 

             Convex lenses - are lenses that are thicker at the middle and thinner at the edge. The light rays that pass through the convex lenses will come together (converge). Parallel rays that strike

                                       the lenses will come together at the focal point of the lens. A straight light rays that passes through the lens will not be refracted.

 

Focal Length

 

                   - is the distance from the centre of the lens or mirror to the focal point.

 

  A mathematical relationship linking the distance of the object in front of the lens to the distance of the image formed by the lens.    

 

                   - if the object is more than two focal lengths in front of the lens, the image is smaller than the object (upside down).

 

                   - if the object is moved closer to the lens so that it is one to two focal lengths away, the image is larger than the object (upside down).

 

                   - if the object is very close , less than one focal length away , the images appear to be located on the other side of the lens and is both upright and larger than the object (upright).

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