Lynde, Carleton John, b. 1872, Gilbert, Alfred C. (Alfred Carlton), 1884-1961 · New Haven, Conn. : A.C. Gilbert Co. · leaf 24
Fig. 26. The light which covers one square at onefoot covers four and nine at two and three feet,and is then only one-fourth and one-ninth asintense GILBERT LIGHT EXPERIMENTS 21 which would cover 1 squareat 1 foot would cover 4and 9 equal squares at 2and 3 feet and would there-fore be one-fourth…
Light · Scientific recreations
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