Thin lenses


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Thin lenses

  1. 1. Thin Lenses By: Emily Earls T’Aundrai Smith
  2. 2. Objectives • • Compare diverging and converging lenses Relate concepts to eyeglasses and contact lenses • Describe the positioning of lenses in compound microscopes and telescopes
  3. 3. Introductory At the end of this lesson, students should be able to tell the difference between converging and diverging lenses. Understand the purpose in eyeglasses and contact lenses and what is different about them. Also, know what the lenses are for in compound microscopes and telescopes.
  4. 4. Diverging & Converging Lenses • • • • The lens with the thicker middle than at the rim is an example of converging lens Converging lenses are used to help with farsightedness(hyperopia). The lens with the thinner middle than it is at the rim is an example of diverging lens Diverging lenses are used to help with nearsightedness(myopia).
  5. 5. Ray Diagrams • • • Ray diagrams for concave lenses inside and outside the focal point give similar results; an erect virtual image smaller than the object Ray diagrams for convex lenses outside the focal point give similar results; a real inverted image Ray diagrams inside the focal point gives a virtual erect image that will be formed
  6. 6. • Real inverted image • Virtual erect image
  7. 7. Positioning of Lenses in a Compound Microscope • • A compound microscope has two types of lenses. It has objective lenses and an ocular lens. The objective lenses are located in the rotating nosepiece, near the object being magnified. Objective Lens • Ocular Lens The ocular lens is located in the part you look through, which magnifies the image.
  8. 8. Positioning of Lenses in a Telescope • • A telescope has two lenses: an objective lens and an eyepiece lens. The objective lens is located at the end of the telescope, and it collects light from a distance and then it brings that image into focus. ● The eyepiece lens takes that focus and magnifies it to make the image or object look bigger to the retina.
  9. 9. Eyeglasses vs. Contact Lenses • Eyeglasses are a frame that holds two pieces of glass or plastic, which have been ground into lenses to correct refractive errors • • Contact lenses are worn directly on the cornea of the eye Eyeglasses and Contacts help with sight by adding or subtracting focusing power to the eye’s cornea and lens
  10. 10. Bibliography • • • • • Craig , F. (2011, March 9). How Telescopes Work. Retrieved October 24, 2013, from Microbus. (2007). The Microscope. Retrieved October 23, 2013, from Nave, C. R. (n.d.). Ray Diagrams for Lenses. Ray Diagrams for Lenses. Retrieved October 28, 2013, from University, O. S. (n.d.). Eye Glasses and Contact Lenses. Eye Glasses and Contact Lenses. Retrieved October 23, 2013, from sses_contact_lenses/Pages/index.aspx