| | ipedia.com: Cone cell Article (Site not responding. Last check: 2007-10-18) |
 | | Cones are less sensitive than the rod cells in the retina (which support vision at low light levels), but allow the perception of color because there are (normally) three kinds of cones, with different photopsins, which have different response curves (that is, they respond to variation in color in different ways). |
 | | They are typically 50 µm long, and their diameter varies from 1.0 to 4.0 µm, being smallest and most tightly packed at the centre of the eye (the fovea). |
 | | The S (blue) cones are sensitive to light at wavelengths shorter than 400 nm, but the lens and cornea of the human eye are increasingly absorbative to these wavelengths, and this sets the lower wavelength limit of human-visible light to approximately 380 nm (the onset of ultraviolet light). |
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