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achromatic achromatic lens analyser angle of incidence beam beats body bright lines called centimetres centre coincidence colours concave mirror conjugate foci convex convex lens corresponding crystal curvature denote diameter direction distance employed equal experiment eye-piece flame focal length fundamental note glass harmonics Hence Iceland-spar incident ray index of refraction interval inversely law of sines lens lenses light luminous point magnifying power medium metres 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 spectra spherical string surface telescope temperature tion tone transmitted traversing tube undulation velocity of sound vertical vibrations per second violet virtual image 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 994 - R' P', SP, will have a constant ratio ; or the sines of the angles of incidence and refraction are in a constant ratio.
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 1028 - Camera. from external objects are first refracted at a convex surface, then totally reflected at the back of the lens, which is plane, and finally emerge through the bottom of the lens, which is concave, but with a larger radius of curvature than the first surface. The two refractions produce the effect of a converging mensicus.
Page 1107 - The statement that the surface of a liquid at rest is a horizontal plane is sometimes expressed in the form "water finds its own level." It is this property of a liquid which enables water to be supplied to a town. A reservoir is constructed on some elevation which is higher than any part of the district to be supplied. Main pipes starting from the reservoir are laid along...
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 1023 - OB in the required points. An eye placed on the other side of the lens will accordingly see a virtual image erect, magnified, and at a greater distance from the lens than the object. This is the principle of the simple microscope. The formula for the distances D, d of object and image from the lens, when both are on the same side, is Fig.
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...
Page 870 - ... 10 minutes the liquid should have acquired a violet-brown colour. If much free gelatin is present the colour makes its appearance more slowly, and assumes a pure brown shade, without any violet. Pure gelatin does not produce any colouration until after the lapse of a few hours.