Sensation and Perception 9th Edition by Bruce Goldstein

Exercise 1

Ellen is looking at a tree. She sees the tree because light is reflected from the tree into her eyes, as shown in Figure. One way to describe this is to say that information about the tree is contained in the light. Meanwhile, Roger is off to the side, looking straight ahead. He doesn't see the tree because he is looking away from it. He is however, looking right at the space through which the light that is carrying information from the tree to Ellen is passing. But Roger doesn't see any of this information. Why does this occur? (Hint #1: Consider the idea that "objects make light visible." Hint #2: Outer space contains a great deal of light, but it looks dark, except where there are objects.)Figure
Ellen sees the tree because light is reflected from the tree into her eyes. Roger doesn't see the tree because he is not looking at it, but he is looking directly across the space where light from the tree is reflected into Ellen's eyes. Why isn't he aware of the information contained in this light?