Light visible and invisible : a series of lectures delivered at the Royal Institution of Great Britain, at Christmas, 1896 (1897)
Thompson, Silvanus Phillips, 1851-1916, Royal Institution of Great Britain · New York : Macmillan · leaf 113
I hold up onthe end of a stick acardboard disk about a foot in diameter coveredwith bright blue paper (Fig. 56). The beams of anelectric lamp are directed upon it to make its tint morebrilliant. You must look at it fixedly while I countthirty in a distinct voice. When I come to thirty Iwill drop… … Fig. 56. II VISIBLE SPKCTRUM AND INK KYI. a red disk you will, when your eye is fatigued, see a greenor peacock coloured ghost. The reason of the contrasttint is that if you have fatigued the eye, or any regionof the retina of the eye, with red waves, that region willbe less sensitive for red than…
Light · X-rays
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