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15.2 Lenses

15.2 Lenses. pp. 568 -579 Mr. Richter. Agenda. Review HW Introduction to Lenses Notes: Types of Lenses Converging Lenses Distances and Images Diverging Lenses. Objectives: We Will Be Able To…. Determine whether an image produced by a lens is real or virtual.

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15.2 Lenses

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  1. 15.2 Lenses pp. 568 -579 Mr. Richter

  2. Agenda • Review HW • Introduction to Lenses • Notes: • Types of Lenses • Converging Lenses • Distances and Images • Diverging Lenses

  3. Objectives: We Will Be Able To… • Determine whether an image produced by a lens is real or virtual. • Determine the orientation and magnification of an image produced by a lens.

  4. Warm-Up: • Where do you see lenses used? What purpose do they serve?

  5. Types of Lenses

  6. Lenses • Curved objects change the direction of light. • Like mirrors, lenses form images, but by refraction instead of reflection. • Images may be real or virtual, depending on distance from the focal length (F).

  7. Types of Lenses Converging Diverging Thicker at the rim than it is at the middle. Edges diverge. • Thicker in the middle than it is at the rim. • Edges converge.

  8. Converging Lenses

  9. Converging Lens Image: Object at Infinity. • All rays of light converge on the focal point. Focuses light energy in one place. No image forms. • Good for burning holes and not much else.

  10. Converging Lens Image Object Closer than Infinity to the Focal Length • Image is real and inverted, and can be projected on to another surface.

  11. Converging Lens Image Object Closer than Infinity to the Focal Length • Image is smaller than object. • Seen in: • Camera lens • Human eye

  12. Corrective Vision: Farsightedness • When the eye cannot move its focal point close enough, nearby images are blurry. • This hyperopia, or farsightedness, can be corrected by a converging lens.

  13. Converging Lens Image Object Closer than Twice the Focal Length • At between twice the focal length and the focal length: • Image is magnified. • Seen in: • movie or slide projector

  14. Converging Lens Image Object At the Focal Length • Rays of light never converge. • Light is projected an infinite distance way. No image forms. • Seen in light houses and search lights

  15. Converging Lens Image Object Closer than the Focal Length • Image is virtual. • Image is projected larger on the same side of the lens as the object. • Good for: • magnifying glass • binoculars

  16. Recap Images of Converging Lenses

  17. Diverging Lenses

  18. Diverging Lenses • Diverging lenses only produce virtual images. • Used to produce upright images that are smaller than the original but a wider viewing angle. • Like: viewfinders in (older) cameras.

  19. Corrective Vision: Nearsightedness • When the eye’s focal point is too close, faraway images are blurry. • This myopia, or near sightedness, can be corrected by a diverging lens.

  20. Wrap-Up: Did we meet our objectives? • Determine whether an image produced by a lens is real or virtual. • Determine the orientation and magnification of an image produced by a lens.

  21. Homework • p. 587-588 #15-18, 21

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