A manual of photographic chemistry, theoretical and practical . ough withoutsuffering refraction. Notice also, that it is at the surface of the bodies that thedeflecting power acts. The ray is bent on entering and bent LENSES. 329 again on leaving; but whilst within the medium it continuesin a straight line. Hence it is evident that by variously modi-fying the surfaces of refractive media the rays of lightmay be diverted almost at pleasure. This will be renderedclear by a few simple diagrams, ^ In the figures following, the dotted lines represent perpen-diculars to the surface at the point whe
A manual of photographic chemistry, theoretical and practical . ough withoutsuffering refraction. Notice also, that it is at the surface of the bodies that thedeflecting power acts. The ray is bent on entering and bent LENSES. 329 again on leaving; but whilst within the medium it continuesin a straight line. Hence it is evident that by variously modi-fying the surfaces of refractive media the rays of lightmay be diverted almost at pleasure. This will be renderedclear by a few simple diagrams, ^ In the figures following, the dotted lines represent perpen-diculars to the surface at the point where the ray falls, and itis seen that the usual law of bending towards the perpendicu-lar on entering, and away from it on leaving the dense medium,is in each case correctly observed. ^ rrz, ±ig. 18, m the last page, termed a prism, bends the ray per-manently to one side ; Fig. 19, consisting of two prisms placedbase to base, causes rays before parallel to meet in a point; andconversely, Fig. 20, having prisms placed edge to edge, divertsthem further
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Keywords: ., bookcentury1800, bookdecade1880, bookidma, booksubjectphotography
