Question

1. define the term intensity. explain its relationship to brightness.
2. explain what rods and cones are, where they are located, and what each one does.
3. what is accommodation?
4. do “the blind spot” test from figure 22.5 on p. 225. why doesnt the blind spot always impair our vision?
5. discuss the process our eye goes through to enable us to see in a dark room.
6. what allows nocturnal animals to see well in the dark?

Explanation:

1. Intensity refers to the amount of energy in light per unit area per unit time. Brightness is a subjective perception related to intensity, with higher - intensity light generally perceived as brighter.
2. Rods and cones are photoreceptor cells in the retina. Rods are more numerous, located mainly in the periphery of the retina, and are sensitive to low - light levels, enabling night vision. Cones are concentrated in the fovea, are responsible for color vision and high - acuity vision in bright light.
3. Accommodation is the ability of the eye to change its focal length to focus on objects at different distances, mainly through the adjustment of the curvature of the lens.
4. The blind spot is the area on the retina where the optic nerve exits, with no photoreceptor cells. It doesn't always impair vision because the brain "fills in" the missing information based on the surrounding visual context and the fact that the blind spots of the two eyes do not overlap completely.
5. In a dark room, the pupils dilate to allow more light in. Rhodopsin in rods is regenerated, increasing their sensitivity to low - light levels, which helps us see in the dark.
6. Nocturnal animals have several adaptations such as a larger number of rods in their retinas, a tapetum lucidum (a reflective layer behind the retina that enhances light sensitivity), and larger pupils to see well in the dark.

Answer:

1. Intensity is the energy of light per unit area per unit time. It is related to brightness as higher intensity is generally perceived as brighter.
2. Rods and cones are photoreceptor cells in the retina. Rods are in the periphery, for night vision; cones are in the fovea, for color and high - acuity vision in bright light.
3. Accommodation is the eye's ability to change focal length by adjusting the lens curvature for different distances.
4. The blind spot is where the optic nerve exits with no photoreceptors. It doesn't always impair vision as the brain fills in and the two eyes' blind spots don't overlap.
5. In a dark room, pupils dilate, and rhodopsin in rods regenerates to increase light sensitivity.
6. Nocturnal animals have more rods, a tapetum lucidum, and larger pupils for good night - vision.