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absorbed achromatic angle of incidence aperture axes axis of double beam blue bodies bright centre CHAP common light concave lens convex lens crown glass crystals curve diameter different colors direction dispersive power diverging rays double refraction equal equation film flint glass focal distance focal length focus F fringes green heat Hence Iceland spar inch incident ray inclination index of refraction lenses luminous negative object glass observed optical orange parallel rays particles pencil perpendicular phenomena placed plane of polarization plane of reflexion plate of glass polarized light polarizing angle position prism prismatic produced radiant point radius ray of light reflected refracted ray refractive power retina rhomb second surface seen shown in fig side spectrum speculum sphere spherical aberration suppose system of rings telescope thickness tint tion transmitted transparent violet rays whence white light yellow
Page 34 - It may also be defined as the sine of the angle of incidence divided by the sine of the angle of refraction, as light passes from air into the substance.
Page 95 - ... parts, the orange 27, the yellow 48, the green 60, the blue 60, the indigo 40, and the violet 80...
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 258 - A new theory of accidental colours is therefore requisite to embrace this class of facts. . " As in acoustics, where every fundamental sound is actually accompanied with its harmonic sound, so in the impressions of...
Page 137 - ... left, or on any other side of it, provided that in all these cases it falls upon the surface in the same manner, or, what amounts to the same thing, the beam of solar light has the same properties on all its sides; and this is true, whether it is white light as directly emitted from the sun, or whether it is red light, or light of any other colour.
Page 255 - With the aid of these facts, the theory of accidental colors will be readily understood. When the eye has been for some time fixed on the red wafer, the part of the retina occupied by the red image is strongly excited, or, as it were, deadened by its continued action.
Page 146 - The index of refraction is the tangent of the angle of polarization.
Page 68 - ... 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...
Page 288 - Delicate observations should not be made when the fluid which lubricates the cornea is in a viscid state. 3. The best position for microscopical observations, is when the observer is lying horizontally on his back. This arises from the perfect stability of his head, and from the equality of the lubricating film of fluid which covers the cornea. The worst of all positions is that in which we look downward vertically.