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The Invisible Spectrum

المؤلف:  GEORGE A. HOADLEY

المصدر:  ESSENTIALS OF PHYSICS

الجزء والصفحة:  p-484

2025-12-21

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The visible spectrum is by no means the limit of the dispersion secured by the prism. Beyond the red are a series of longer waves that can easily be detected as heat rays, while beyond the violet are shorter waves that have great chemical activity, and are called the chemical or actinic rays.

Demonstration. -Cut a piece of photographic printing paper into strips and pin them end to end upon the wall of a dark room so as to form a long strip. By means of a prism throw the solar spectrum upon the middle of the strip, which should extend a third of its length beyond each end of the spectrum. Mark the position of every color and the end of the visible spectrum. After a short exposure notice that the greatest effect on the paper is at the violet end of the spectrum or just beyond it, and that at the red end there is practically no change.