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analyser angle of incidence beam beats body bright lines called centimetre centre coincide colours concave mirror conjugate foci convex convex lens crystal curvature denote diameter direction distance employed equal experiment eye-piece flame focal length frequency of vibration fundamental note glass harmonics Hence Iceland-spar incident ray index of refraction interval inverted law of sines lens lenses luminous point magnifying power medium metres metres per second millimetre minimum deviation nearly node normal number of vibrations object object-glass oblique observer obtained octave optical ordinary parallel particles pencil perpendicular pipe pitch placed plane mirror plate polarization portion position principal axis principal focus prism produced propagation radius rarefaction ratio reflected ray refrangibility represented retina rotation screen seen side slit solar spectra spectrum spherical string surface telescope temperature tion tone transmitted traversing tube undulation velocity of sound vibrations per second visual angle wave-front wave-length waves
Page 996 - 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.
Page 1044 - B' to infinite distance, F will be the principal focus of both lenses, and the magnification is the ratio of the focal length of the object-glass to that of the eye-piece.
Page 962 - ... theory of light was proposed. This new explanation was at first almost as simple as the former. But it failed to account for the fact proved by experiment that the aberration was unchanged when observations were made with a telescope filled with water. For if the tangent of the angle of aberration is the ratio of the velocity of the earth to the velocity of light, then, since the latter velocity in water is three-fourths its velocity in a vacuum, the aberration observed with a water telescope...
Page 1150 - The Comprehensive English Dictionary, EXPLANATORY, PRONOUNCING, AND ETYMOLOGICAL. Containing all English Words in present use, numerous Phrases, many Foreign Words used by English Writers, and the more important Technical and Scientific Terms. BY JOHN OGILVIE, LL.D.
Page 1000 - By raising or lowering the prism in its stand (Fig. 696), 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 its top is usually covered with a movable plate of blackened metal, having a semicircular notch at one edge, for the observer to look through.
Page 1027 - It is a kind of tent surrounded by opaque curtains, and having at its top a revolving lantern, containing a lens with its axis horizontal, and a mirror placed behind it at a slope of 45°, to reflect the transmitted light downwards on to a sheet of white paper lying on the top of a table.
Page 999 - Fig. 656, 657, is one of the commonest. The essential part is a totally-reflecting prism with four angles, one of which is 90°, the opposite one 135°, and the other two each 67° 30'.
Page 1120 - ... from 50° to 60° with the normal, it is more or less polarized, and in like manner a reflector composed of any of these substances may be employed as an analyzer. In so using it, it should be rotated about an axis parallel to the incident rays which are to be tested, and the observation consists in noting whether this rotation produces changes in the amount of reflected light. Mains
Page 1009 - A' = angle between normals = angle of prism. Again, the deviation A 0 A', being the angle at the centre of a circle, is measured by the arc A A', which subtends it. To obtain the minimum deviation, we must so arrange matters that the angle ABA' being given (= angle of prism), the arc A A