A treatise on optics

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Lea & Blanchard, 1841 - Science - 418 pages
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Page 143 - ... one of the most interesting, as well as one of the most perfect, of the physical sciences.
Page 120 - Even the most transparent bodies in nature, aw and water, when in sufficient thickness, are capable of absorbing a great quantity of light. On the summit of the highest mountains, where their light has to pass through a much less extent of air, a much greater number of stars is visible to the eye than in the plains below; and through great depths of water objects become almost invisible.
Page 26 - The perpendicular being drawn, the refracted ray is connected with the incident, by the law (p. 29, text*) that the sine of the angle of refraction bears a constant ratio, for a given medium, to the sine of the angle of incidence. To represent this law analytically, suppose a ray passing from a rarer to a denser medium, call the angle of incidence 0, the angle of refraction...
Page 137 - B' that the latter has at the sides C' and D', as shown in Jig. 81. ; or, in general, that the diameters of the beam, at the extremities of which the beam has similar properties, are at right angles to each other, as A' B' and C
Page 85 - A focus of violet light concentrated by a lens 1-2 inches in diameter, and 2-3 inches in focal length, was made to traverse one half of the needle 200 times; and though this experiment was repeated with different needles at different seasons of the year, and different hours of the day, yet the duration of a given number of oscillations was almost exactly the same after as before the experiment. Their attempts to verify the results of Baumgartner were equally fruitless; and they therefore consider...
Page 13 - The word speculum is used to describe a reflector which is metallic, such as those made of silver, steel, or of grain tin mixed with copper. (10.) Specula or mirrors are either plane, concave, or convex. A plane speculum is one which is perfectly flat, like a looking-glass ; a concave speculum is one which is hollow like the inside of a watch-glass ; and a convex speculum is one which is round like the outside of a watch-glass. As the light which falls upon glass mirrors is intercepted by the glass...
Page 28 - ... medium, as out of water into air, the angle of incidence is less than the angle of refraction: and these angles are so related to one another, that when the ray which was refracted in the one case becomes the incident ray, what was formerly the incident ray becomes the refracted ray. (29.) In order to discover the law, or rule, according to Fig.
Page 221 - French coast, which is about 40 or 50 miles distant, as distinctly as through the best glasses. The sailors and fishermen could not at first be persuaded of the reality of the appearance ; but as the cliffs gradually appeared more elevated, they were so convinced that they pointed out and named to Mr. Latham the different places which they had been accustomed to visit : such as the bay, the windmill at Boulogne, St.
Page 137 - IF we transmit," says Dr. Brewster, " a beam of the sun's light through a circular aperture into a dark room, and if we reflect it from any crystallized or uncrystallized body, or transmit it through a thin plate of either of them, it will be reflected and transmitted in the very same manner and with the same intensity, whether the surface of the body is held above or below the beam, or on the right side or left, or on any other side of it, provided that in all these cases it falls upon the surface...
Page 29 - This amounts to the same with saying, that, in the case before us, the sine of the angle of incidence is to the sine of the angle of refraction in a given ratio.

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