Civil Engineering Reference
In-Depth Information
FIGURE 4.1
The structure of the eye.
series so that the incoming light energy is “amplified,” but since the receptor area is
increased, there is a loss in resolution (see Figure 4.3).
A driver at nighttime can notice many of the effects of the visual system. As it gets
darker, the color vision is lost, since the cones, which have low sensitivity, are no longer
active. The incoming light energy is not enough to excite the cones so the driver relies on
the rods in his peripheral vision. An experienced nighttime driver, such as a truck driver,
will sometimes turn his head to the side. In this way he can focus the image directly on
the peripheral field of vision (the rods) rather than the central. This will enhance his
sensitivity, and he can see the road ahead more clearly.
