Optics: Light and Sight Theoretically and Practically Considered, with Their Application to Fine Art and Industrial Pursuits

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Strahan & Company, 1870 - 268 páginas
 

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160's SUPERB on lens development history

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Página 6 - 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.
Página 67 - ... test of difference of refrangibility : and the conclusion deduced by Newton is no longer admissible as a general truth : " That to the same degree of refrangibility ever belongs the same color, and to the same color ever belongs the same degree of refrangibility." By absorbing the excess of any color at any point of the spectrum above what is necessary to form white light, we may actually cause white light to appear at that point, and this white light will possess the remarkable property of remaining...
Página 94 - Thus, if the light be homogeneous, a bright line of light will be formed under the centre of the opaque object AB, outside which will be dark lines, and then bright and dark lines alternately. If the arrangement of these lines be examined, they will be found to be hyperbolic, as exhibited in Jig.
Página 66 - ... very little of the violet. The yellow space, which has not been much absorbed, has increased in breadth. It occupies part of the space formerly covered by the orange on one side, and part of the space formerly covered by the green on the other. Hence it follows that the blue glass has absorbed the red light which, when mixed with the yellow light, constituted orange, and has absorbed also the blue light which, when mixed with the yellow, constituted the part of the green space next the yellow.
Página 65 - Coloured fluids, such as black and red ink, though equally homogeneous, stop or absorb different kinds of rays, and when exposed to the sun they become heated in different degrees ; while pure water seems to transmit all the rays equally, and scarcely receives any heat from the passing light of the sun. When we examine more. minutely the action of...
Página 227 - Having focussed the object, replace a, and gradually close the slit till a good spectrum is obtained. The spectrum will be much improved by throwing the object a little out of focus. Every part of the spectrum differs a little from adjacent parts in refrangibility, and delicate bands or lines can only be brought out by accurately focussing their own parts of the spectrum.
Página 34 - ... as follows. From the distance between the image and the object in feet, subtract the focal distance of the lens in feet, and divide the remainder by the same focal distance. By this quotient divide twice the distance of the object in feet, and the new quotient will be the magnifying power, or the number of times that the apparent magnitude of the object is increased. When the focal length of the lens is quite inconsidertble, compared with the distance of the object, as it is in most cases, the...
Página 66 - ... the middle of the red space, the whole of the orange, a great part of the green, a considerable part of the blue, a little of the indigo, and a very little, of the violet...
Página 97 - ... to tell us that water consists of 1 part of hydrogen by weight united with 8 parts of oxygen; that marble is composed of 56 parts of lime, and 44 of carbonic acid; common salt, of 35J parts of chlorine, and 23 of sodium ; turpentine, of 30 carbon, and 4 hydrogen ; chloroform, of 12 carbon, 1 hydrogen, and 106} chlorine.
Página 213 - When the chimney is put together, the upper end of the bottom piece is inserted about | an inch into the cone of the next piece above, and fixed there by three ties or pins, so that the two pieces are firmly held together ; but there is still plenty of airway, or entrance into the chimney between them. The same arrangement holds good with each succeeding piece. When the ventilating chimney is fixed in its place, it is adjusted, so that the lamp-chimney enters about...

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