The document summarizes how light detection and vision work. Rods and cones in the retina detect light and send signals through the optic nerve to the brain. Rods function in dim light and detect black and white, while cones function in bright light and detect color. The highest concentration of cones is in the fovea centralis, allowing for sharpest vision. There is a blind spot where the optic nerve enters the eye containing no photoreceptors. The brain interprets the signals from the eyes to produce the correct orientation and size of images.

1. Light detection

4. Photoreceptors (retina) Connected to nerve-endings from optic nerve Nerve conveys impulses to brain when stimulated 2 kinds: Rods Cones

5. Question: Have you experienced occasions when you are not able to see for a short period of time? When does this situation normally take place?

6. Rods Contain visual purple Pigment concerned with vision in dim light Light detection by visual purple by bleaching From bright  dark place unable to distinguish objects for a while (because takes time for visual purple to reform) Requires vitamin A (deficiency  night-blindness)

7. Cones Less sensitive to light Inefficient in dim light Concerned with bright light and c o l o u r vision 3 types: (each contain a different pigment) Red Blue Green Pigments absorb light of different wavelengths Taken together, cones allow us to see spectrum of colours

10. yellow spot where images are normally focused highest conc. of cones vision sharpest in bright light No photoreceptors (not light sensitive) blind spot formation

11. Fovea centralis yellow spot where images are normally focused only contains cones concentration of cones highest at this point Therefore vision is sharpest in bright light when images are focused onto the yellow spot

12. Blind spot found immediately over optic nerve where it enters the eye has no photoreceptors (not sensitive to light) Blind spot

13. Vision

14. Formation of image on retina http:// www.bausch.com/us/vision/teens/illusions/eyeworks.jsp

15. Image formed on retina Inverted (upside down) Reversed (back to front) Diminished (smaller in size than the object being observed)

17. What are the similarities between the eye and a camera?

18. Processing by brain Impulses produced by light falling on the rods and cones are transmitted via the optic nerves to rear of cerebrum Brain interprets these impulses so we see the object the right way up and the right size