a. the fovea

b. the lens

c. the sclera

d. the cornea

e. the iris

Answer: D - the cornea does about 2/3 of the focusing

2. On its way to the retina, light has to pass through a network of blood vessels inside the vitreous humour, but we never see these blood vessels. Why not? (10 words or less)

Answer: because blood vessels don't move relative to the retina and stabilized images fade

3. [TRUE or FALSE] At night, your vision is best not in the center of your vision, but a little off to the side.

Answer: TRUE

4. [TRUE or FALSE] Your color vision is best in the fovea.

Answer: TRUE

5. [TRUE or FALSE] If the focal length of your lens is too short, this can be remedied by adding a concave lens in front of your eye.

Answer: TRUE

6. [TRUE or FALSE] Humans can reliably detect even a single photon of light.

Answer: TRUE

7. [TRUE or FALSE] Tomatoes look red because they absorb red light.

Answer: FALSE - Tomatoes look red because they reflect red light.

8. Visual transduction is the most important job of the retina. In transduction

a. electrical energy is converted into chemical energy

b. chemical energy is converted into light energy

c. light energy is converted into neural signals

d. electrical light energy is conducted by the brain

e. all of the above

Answer: C

9. (2 points) Why do you get "red-eye" when you take photos with a flash? (25 words or less)

Answer: The back of the retina is actually reddish. Light from the flash travels inside the pupil, and red light is reflected back to the camera.