Text: Rays corresponding to this infinite variety of colour must, therefore, exist together in white solar light, and these rays differ physically from one another in the rapidity of the vibrations of which they consist; the deep crimson corresponding to less than 400,000,000,000,000 vibrations per second, and the extreme violet to more than 700, 000,000,000,000, the length of a wave in air being, in the first case, about 1/39,000 of an inch, and, in the second case, 1/68,000 of an inch. (from Maxwell biography, page 234)

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