1. Lens Technologies & the Human Eye
12.3
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2. Refracting Telescopes: Galileo and Kepler

3. Reflecting Telescope - Newton
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Reduces chromatic aberration

4. Binoculars 2 refracting telescopes
Reflection through prisms lengthens the light path, increasing magnification
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5. Microscopes
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6. Structure – Human Eye

7. Focussing – Human Eye
Ciliary muscles make the lens shorter and thicker to focus a nearby object
Relaxed eye lens focusses on a distant object

8. Eye vs. Camera

9. Correcting Vision Using Lenses
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Near-sightedness; eyeball too long, so image forms in front of retina.

10. Hyperopia
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Far-sightedness; eyeball too short, so rays reach retina before they meet.

11. Presbyopia Lenses become stiff with age, cannot change shape
Can’t focus on nearby objects.

12. Astigmatism
Blurred or distorted vision caused by incorrectly shaped cornea.
Part of an image may be in focus, but the rest is blurry.
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