Elementary Treatise on Natural Philosophy, Volumen4 |
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Elementary Treatise on Natural Philosophy: Sound and light Augustin Privat-Deschanel Vista completa - 1872 |
Términos y frases comunes
analyser angle of incidence beam bright lines called centre of curvature coincide colours concave concave lens conjugate conjugate points convex lens crystal denote diameter direction displacement distance emergent employed equal equation experiment eye-piece flame focal length foci fundamental tone gives glass Hence homographic Iceland-spar image formed incident ray index of refraction interval inverted lenses light magnification magnifying power medium minimum deviation node normal number of vibrations object object-glass oblique observer obtained octave opposite optical ordinary P₁ parallel particles pass pencil perpendicular pipe pitch placed plane mirror plate polarization portion position principal focus principal plane prism produced propagation radius rarefaction ratio reflected ray represented rotation screen seen side slit solid angle spectra spectrum spherical string subtends surface telescope thickness tion traversing tube velocity of sound vertical vibrations vibrations per second visual angle wave-front wave-length waves
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Página 129 - When a ray of light passes from one medium to another, it is refracted so that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is equal to the ratio of the velocities in the two media.
Página 147 - Thus each transparent medium has its own particular refracting power, but for the same transparent medium the ratio of the sines of the angles of incidence and refraction is always the same.
Página 133 - By raising or lowering the prism in its stand (Fig. 657), the image of the object to be sketched may be made to coincide with the plane of the paper. The prism is mounted in such a way that it can be rotated either about a horizontal or a vertical axis; and...
Página 252 - Mirage. — An appearance as of water is frequently seen in sandy deserts, where the soil is highly heated by the sun. The observer sees in the distance the reflection of the sky and of terrestrial objects, as in the surface of a calm lake (Fig.
Página 176 - ... either case, the thickness of the lens being neglected, the visual angle is the angle which the object subtends at the centre of the lens, and therefore varies inversely as the distance of this centre from the object. For lenses of small focal length, the reciprocal of the focal length may be regarded as proportional to the magnifying power. Simple Microscope. — By a simple microscope is usually understood a lens mounted in a manner convenient for the examination of small objects.
Página 98 - Photometry. — Photometry is the measurement of the relative amounts of light emitted by different sources. The methods employed for this purpose all consist in determinations of the relative distances at which two sources produce equal intensities of illumination. The eye would be quite incompetent to measure the ratio of two unequal illuminations; but a pretty accurate judgment can be formed as to equality or inequality of illumination, at least when the surfaces compared are similar, and the...
Página 291 - ... and the quartz or saccharine solution is then introduced, there is a partial restoration of light. On rotating the analyzer through a certain angle, there is again complete extinction of the light; and on comparing different plates of quartz, it will be found that the angle through which the analyzer must be rotated is proportional to the thickness of the plate. In the case of solutions of sugar, the angle is proportional jointly to the length of the tube and the strength of the solution. The...
Página 247 - AF distances travelled in the same time in the two media. Hence the sines of the angles of incidence and refraction are directly as the velocities of propagation of the incident and refracted light. The relative index of refraction from one medium into another is therefore the ratio of the velocity of light in the first medium to its velocity in the second; and the absolute index of refraction of any medium is inversely as the velocity of light in that medium.
Página 19 - Colladon, in 1826, at the Lake of Geneva. Two boats were moored at a distance of 13,500 metres (between 8 and 9 miles). One of them carried a bell, weighing about 140 Ibs., immersed in the lake. Its hammer was moved by an external lever, so arranged as to ignite a small quantity of gunpowder at the instant of striking the bell. An observer in the other boat was enabled to hear the sound by applying his ear to the extremity of a trumpetshaped tube (Fig.
Página 20 - ... having its lower end covered with a membrane and facing towards the direction from which the sound pro•ceeded. By noting the interval between seeing the flash and hearing the sound, the velocity with which the sound travelled through the water was determined. The velocity thus computed was 1435 metres per second, and the temperature of the water was 8°*1 C.