OCR Text |
Show Why One Cannot See So . Well in Glaring Light An observant chauffeur, passing an automobile with glaring headlights, noted that objects at the side of the road which had been distinctively visible vis-ible dropped out of sight when the bright lights were thrown upon them. Since one can see better in a little light than in no light, he wondered, why can one not see better in brinj'jt light than In moderate light? The answer is, paradoxically, that the less light there is the better one sees, for the brighter the object the less efficient Is the eyesight. If, after we have been in darkness, we suddenly sudden-ly turn on a bright light and look at our eyes in the mirror, we can see the pupil of the eye rapidly growing smaller. If we reduce the light the pupil dilates again. What happens Is the same as in the camera when we adjust the shutter to the Intensity of the light. The colored iris of the eye corresponds corre-sponds to the shutter. It consists chiefly of a muscle which, as the light increases, Is stimulated to contract, thus drawing the curtain and shutting out some of the superfluous light. It usually takes a few seconds for this adjustment to take place. Thus when we emerge from darkness into light we are blinded until the Iris can shut out some of the light from the eyes. |