I saw red…

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No Warrant or Cherry Pie, but as I was studying for my commercial pilot test one of the questions was what part of the eye needs to adjust for night vision and how long does it take?

Anyone know? Do you even know the parts of the eye? I didn’t! Well here you go Rods, Cones, Retina…know which one now or how long to adjust your eyes?

The answer is 30 minutes and its the Rods.

  • The light response of the rods peaks sharply in the blue; they respond very little to red light. This leads to some interesting phenomena:

    Red rose at twilight: In bright light, the color-sensitive cones are predominant and we see a brilliant red rose with somewhat more subdued green leaves. But at twilight, the less-sensitive cones begin to shut down for the night, and most of the vision comes from the rods. The rods pick up the green from the leaves much more strongly than the red from the petals, so the green leaves become brighter than the red petals!

    The ship captain has red instrument lights. Since the rods do not respond to red, the captain can gain full dark-adapted vision with the rods with which to watch for icebergs and other obstacles outside. It would be undesirable to examine anything with white light even for a moment, because the attainment of optimum night-vision may take up to a half-hour. Red lights do not spoil it.

    These phenomena arise from the nature of the rod-dominated dark-adapted vision, called scotopic vision.

Now with that bit of knowledge under your belt try this on…

Kinda cool how at the end of the day as it gets dark the sky reddens and then dusk turns to dark and then to night. The cool fact is that the wind-down from day to night happens through the shades of red so our eyes can adjust. Hmmm think God mighta done that on purpose?!

Cool to me!

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