Tuesday, December 6, 2011

night vision

Human night vision is quite poor as compared to other animals.  The cells in the eye that are responsible for night vision are the rod cells.  The eyes take quite an amount of time to adjust to the night vision.  The first adaptaion takes place after about 10 minutes and the second takes about 30 minutes.  But even with this half hour adjustment to night vision human vision is still far worse than most animals because of a layer of tissue called the tapetum lucidum. This tissue reflexs light back to the retina thus increasing the amount of light taken in by the eye and increasing the ability to see at night.  This is why humans see so poorly at night. 

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