Gage, Alfred P. (Alfred Payson), 1836-1903 · Boston, London, Ginn · leaf 348
Fig. 230. 289. The Bunsen photometer (Fig. 2.30) has a screen ofpaper, S, mounted in a box, B, open in front and at thetwo ends. The box slides on a graduated bar. The screenhas a circular central spot saturated with paraffine, whichrenders the spot more translucent than other portions of… … Fig. 231. a Standard candle, L. When the screen is so placed thatthe two sides are equally illuminated by the two lights, theparaffined spot becomes nearly invisible. When one side ismore strongly illuminated than the other, the spot appearsdark on that side and light on the other. The candle…
Physics
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