Word: centralisation
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The cause is a simple optical principle. The burning effect of the bomb's heat on exposed skin diminishes as the square of the distance (twice as far away, it is one-fourth as strong). But the eye is a lens that concentrates heat and light in a spot...
Sharp vision and color vision have two other common denominators. One is a highly sensitive dimplelike spot on the retina (the fovea centralis-literally, "central pit"), which acts as a magnifying device to spread the image over a greater number of visual cells. In this dimple, common to the vertebrates...
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