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The pupil of the human eye can range in size from 2 mm to over 8 mm to adapt to the environment. The human eye can detect a luminance from 10 −6 cd/m 2, or one millionth (0.000001) of a candela per square meter to 10 8 cd/m 2 or one hundred million (100,000,000) candelas per square meter.
The highest such number that the eye can resolve as stripes, or distinguish from a grey block, is then the measurement of visual acuity of the eye. For a human eye with excellent acuity, the maximum theoretical resolution is 50 CPD [43] (1.2 arcminute per line pair, or a 0.35 mm line pair, at 1 m).
The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth. The human eye can distinguish about 10 million colors. [3]
According to CNN, Dr. Gary Heiting, a licensed optometrist and senior editor of All About Vision explained why all human eyes are actually brown, no matter if they look blue or greenish.
The human eye, showing the iris and pupil. In 1802, philosopher William Paley called it a miracle of "design."In 1859, Charles Darwin himself wrote in his Origin of Species, that the evolution of the eye by natural selection seemed at first glance "absurd in the highest possible degree". [3]
As absurd as it can sound on paper, the truth is that facts are just fun, the more obscure, weird and random, the better. After all, everyone needs a handful of interesting trivia to pull out at ...
Each human eye contains 120 million rods. Cones are found primarily in the center (or fovea ) of the retina. [ 25 ] There are three types of cones that differ in the wavelengths of light they absorb; they are usually called short or blue, middle or green, and long or red.
The pupil is a hole located in the center of the iris of the eye that allows light to strike the retina. [1] It appears black because light rays entering the pupil are either absorbed by the tissues inside the eye directly, or absorbed after diffuse reflections within the eye that mostly miss exiting the narrow pupil.