PSYCO104 Lecture 17: Lecture 17
8 Nov 2016
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500 times more sensitive to light than cones. Cones have single line connection (one to one) Create blind spot where optic nerve exits from eye. Absorption of light changes rate of nt release. Greater rate of release = stronger signal passed on. Human visual system adapted for both low and high light conditions. So(cid:373)e a(cid:374)i(cid:373)als(cid:859) (cid:448)isual syste(cid:373)s desig(cid:374)ed to o(cid:374)ly see at day or (cid:374)ight. Dark adaptation: progressive improvement in brightness sensitivity in low lighting condition. Rods adapt after 30 min: can detect light intensities 1/10000 as great as b4 adaptation. Rods not sensitive to wavelengths of red light (remain dark adapted) and therefore can go from red light to dim/dark conditions. Screens on most electronics (cid:894)s(cid:373)art pho(cid:374)es, (cid:272)o(cid:373)puters, tv(cid:859)s) emit light in the blue spectrum. Exposure to this blue light reduces melatonin production (hormone important in reg sleep) This likely has evolutionary origins (blue sky earlier in the day, red at night during sunset)
