Oldal 54 [54]
OCR
30 LIGHT AND WATER so that unless the ripple is very gentle, the image is soon lost. The position of the spectator in the figure (Fig. 12) is so chosen that he can see little but the near sides and the crests of the waves, and indeed this is generally the case when one is standing close to a sheet of water and looking at a gently rippled surface at a little distance. he line of vision is so nearly parallel to the level of the water that the far sides of the waves are out of sight. The objects on the opposite shore are seen reflected in the crests of the waves (supposing always that they would be visible in that part of the water, if smooth) and between these glimpses of the image the sky appears by reflexion on the tilted surfaces. If the water is much agitated, or if one is looking in a virtually hortzontal direction, as at distant waves from a position near the level of the lake, one sees nothing but their near sides, and therefore in all probability only reflected sky light.’ " In any wave-section (as in Figs. 12 or 13) there is of course only one point on the crest of each wave—z.e., the summit—where . the normal is vertical, and where a ray would therefore be reflected as on a horizontal plane. But on either side of this point there is a short piece of the curve where the normals are nearly vertical, and which would reflect rays to the eye from points close above or below the point which is seen reflected in the summit. ‘Thus a conspicuous white object, such as the side of a house, gives patches or strips of white light on the crests of the waves. It is perhaps unnecessary to warn the reader that if he could see a definite image of any object in the curved side of a wave, it would be a very distorted one (and in a concave surface an erect, instead of an inverted, image). As a matter of fact, this is hardly ever possible, and moreover does not at all concern us in the present discussion, as we are considering the combined effect of the re
