Question

chapter 15 multiple choice question 3
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which of the following is the best explanation of why it is difficult to discriminate the color of an object at night?
○ cones come in three types, each sensitive to different wavelengths of light.
○ as many as 100 cones may converge on one ganglion cell.
○ at night, the amount of light entering the eye is insufficient to stimulate the cone cells but is sufficient to stimulate the rod cells.
○ the foveae are densely packed with cones.

Explanation:

To determine the best explanation, we analyze the role of cones (color vision) and rods (low - light vision) in the eye. At night, the light level is low. Cone cells are responsible for color vision but need relatively high light levels to be stimulated. Rod cells are more sensitive to low light.

• The first option just describes the types of cones, not why color discrimination is hard at night.
• The second option is about the convergence of cones on ganglion cells, which is not related to night - time color discrimination difficulty.
• The fourth option is about the foveae's cone density, which doesn't explain the night - time color issue.
• The third option correctly states that at night, the light is insufficient to stimulate cone cells (needed for color) but enough for rod cells (which don't distinguish color), so it explains the difficulty in color discrimination.

Answer:

C. At night, the amount of light entering the eye is insufficient to stimulate the cone cells but is sufficient to stimulate the rod cells.