A Treatise on New Philosophical Instruments for Various Purposes in the Arts and Sciences: With Experiments on Light and Colours, Volumen1Archibald Constable and Company, 1813 - 427 páginas |
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Términos y frases comunes
accuracy achromatic acid angle of incidence angle subtended arch axis balsam Canada balsam centre CHAP chromate of lead constructed convex lens corrected crown glass depolarising diameter dispersive power distance distinct vision double refraction Dr Wollaston employed equal experiments extreme eye-glass eye-piece Feet fibres flint glass fluid focal length focus fringes goniometer greatest refraction Hence Iceland spar inches index of refraction instrument ject Juice lens lenses light luminous points magnifying power mean ray measure the angle ment mica micrometer microscope Minutes motion moveable muriatic object glass observation obtain oil of cassia parallel perpendicular placed plane polarised position principle prism produced radius realgar reflected refracting angle refractive power refrangible rays rock crystal scale screw semilenses spectrum formed standard prism steel points substances sulphur surface Table telescope tion transparent tube uncorrected colour uncorrected green vernier vertex violet wires
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Página 303 - The agate is very transparent, and gives a distinct image of any luminous object; but on each side of this image is one highly coloured, forming with it an angle of several degrees, and so deeply affected with colour that no prism of agate, with the largest refracting angle, could produce an equivalent dispersion. Upon examining this coloured image with a prism of Iceland spar, I was astonished to find that it had acquired the same property as if it had been transmitted through a doubly refracting...
Página 208 - Lakes are not subject to tides ; at least the amount of tide, so far as observation goes, seems not to be ascertained. The remarkable transparency of certain lakes is truly astonishing ; thus the waters of Lake Superior are so pellucid, that, according to Mr. Heriot, the fish and rocks may be seen at a depth incredible to persons who have never visited these regions. The density of the medium on which the vessel moves appears scarcely to exceed that of the atmosphère, and the traveller becomes impressed...
Página 304 - ... its laminae parallel to those of the former, the light will find an easy passage through the second plate ; but if the second plate has its laminae perpendicular to those of the first, the- light will be wholly reflected, and the luminous object will cease to be visible.
Página 297 - The first of these pencils is said to experience the usual or ordinary refraction, and the other the unusual or extraordinary refraction. If the luminous object from which the ray...
Página 217 - ... medium. Since the range of inclination within which total reflection takes place, depends not only on the density of the reflecting prism, but also on the rarity of the medium adjacent to it, the extent of that range varies with the difference of the densities of the two media. When, therefore, the refractive power of one medium is known, that of any rarer medium may be learned, by examining at what angle a ray of light will be reflected from it. For instance, when any object is laid under a...
Página 217 - Its application in the first instance is deduced from a theorem, from which we gather, that since the range of inclination within which total reflection takes place, depends not only on the density of the reflecting prism, but also on the rarity of the medium adjacent to it, the extent of that range will vary according to the difference of the densities of the two media.
Página 374 - We cannot expect any essential improvement in that instrument, unless from the discovery of some transparent substance, which, like the diamond, combines a high refractive power with a low power of dispersion."* This substance has subsequently been formed into lenses by Mr.
Página 208 - I could see perfectly well to write or read ; much more to fasten or lay hold on any thing under us that was to be taken up. And, by the return of the air-barrels, I often sent up orders written with an iron pen, on small plates of lead, directing how to move us from place to place as occasion required. At other times, when the water was troubled and thick, it would be as dark as night below ; but in such...
Página 298 - ... into two ; and when the eighth part of a revolution is completed, the whole of each of the pencils is divided into two portions. When the fourth part of a revolution is completed, the pencil refracted in the ordinary way by the first crystal will be refracted in the extraordinary way only by the second, and the pencil refracted in the extraordinary way by the first will be refracted in the ordinary way only by the second : so that the four pencils will be again reduced to two. At the end of...
Página 216 - ... that the ratio of the sines of the angles of incidence and refraction is constant for refraction in the same medium, was effected by Snell and Descartes.