1. Minds-on

4. The Human Eye

6. The Eye vs. the Camera The EyeThe Camera Opens and closes to adjust the amount of light that enters The IrisThe diaphragm

7. The Eye vs. the Camera The EyeThe Camera The opening where light enters The pupilThe Aperture

8. Dilated pupil: when in dim light Constricted pupil: when in bright light

9. The Eye vs. the Camera The EyeThe Camera Refract light to form a smaller, sharp image The lens and cornea The lens

10. The Eye vs. the Camera The EyeThe Camera Surface where the image is created retinaFilm or digital sensor

11. Photoreceptor cells on Retina - Rod cells: detect object in low light; we see shades of grey - Cone cells: detect colors

12. The Cornea-lens combination concentrates light to form a smaller, inverted and real image on the retina. How the Brain ‘Sees’ Any question at this point?

13. Electrical impulses from the retina travel through the optical nerve to the brain, where the image is flipped so we ‘see’ upright.

14. Accommodation: Changes the focal length of the lens by changing the lens shape(using eye muscles) so that both close and distant objects can be seen clearly.

15. Focusing Problems Hyperopia (Far-Sightedness) Disability: can’t focus near objects. Cause: eyeball is too shallow Image forms: beyond retina Correct with: A converging lens

16. The converging lens, causes the light rays to intersect sooner so that the image focuses on the retina instead of beyond the retina.

17. A positive meniscus is a thinner converging lens used in glasses.

18. Focusing Problems Myopia (Near-Sightedness) Disability: can’t focus distant objects. Cause: eyeball is too deep Image forms: in front of retina Correct with: A diverging lens

19. The diverging lens, causes the light rays to intersect later so that the image focuses on the retina instead of in front of the retina.

20. A negative meniscus is a thinner diverging lens used in glasses.

21. Focusing Problem Presbyopia Disability: can’t focus near objects (small print) due to poor accomodation. Cause: aging lens is less elastic, eye muscles are weaker Lens does not thicken enough Image forms: beyond retina Correct with: A converging lens for reading

22. For Presbyopia: The converging lens, causes the diverging light rays (from close objects) to intersect sooner so that the image focuses on the retina instead of beyond the retina.

23. Other Focusing Problems

24. Astigmatism

25. Colour Blindness

26. Cataracts Cataract = a medical condition in which the lens of the eye becomes progressively opaque, resulting in blurred vision.

27. Tunnel Vision a condition in which you can see things that are straight ahead of you but not to the side (i.e. loss of peripheral vision)

28. Eye blood vessels burst