# Elementary Treatise on Natural Philosphy: Sound and light

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Page 911 - 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 910 - SP, will have a constant ratio; or the sines of the angles of incidence and refraction are in a constant ratio. It is often referred to as the law of sines. The angle by which a ray is turned out of its original course in undergoing refraction is called its deviation. It is zero if the incident ray is normal, and always increases with the angle of incidence.
Page 959 - A 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 1072 - The object of these primers is to convey information in such a manner as to make it both intelligible and interesting to very young pupils, and so to discipline their minds as to incline them to more systematic after-studies. They are not only an aid to the pupil, but to the teacher, lightening the task of each by an agreeable, easy, and natural method of instruction.
Page 1069 - In the present work I have surveyed the Teaching Art, as far as possible, from a scientific point of view ; which means, among other things, that the maxims of ordinary experience are tested and amended by bringing them under the best ascertained laws of the mind.
Page 917 - As the paper, for convenience of drawing, must be at a distance of about a foot, a concave lens, with a focal length of something less than a foot, is placed close in front of the prism in drawing distant objects. By raising or lowering the prism in its stand (Flo.
Page 790 - ... 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.
Page 1072 - They are not only an aid to the pupil, but to the teacher, lightening the task of each by an agreeable, easy, and natural method of instruction. In the Science series some simple experiments have been devised, leading up to the chief truths of each science. By this means the pupil's interest is excited, and the memory is impressed so as to retain without difficulty the facts brought under observation. The wood-cuts which illustrate these primers serve the same purpose, embellishing and explaining...
Page 1072 - NICHOL. (OtJiera in preparation.) The object of these Primers is to convey information in such a manner as to make it both intelligible and interesting to very young pupils, and so to discipline their minds as to incline them to more systematic after-studies.
Page 892 - It thus appears, that, when a plane mirror is rotated in the plane of incidence, the direction of the reflected ray is changed by double the angle through ivhich the mirror is turned.