Stranica 49 [49]
OCR
CHAPTER II REFLEXIONS IN RIPPLED WATER HE absolutely smooth surface thus far assumed, giving a perfect, but lifeless, reflexion of neighbouring objects, is not often met with except in small ponds orin sheltered corners. A sheet of water of any extent is almost always in more or less motion, the amount of which varies with the strength of the breeze. It is the gentler motions that give rise to the most beautiful and characteristic reflexions; and for the consideration of these we will now suppose there to be a slight disturbance of the water, strong enough to ripple its surface, but not so strong as to destroy all form of the image. The following simple experimentwill serve to illustrate what occurs under the new conditions. Leta small looking-glass be laid flat on the table, so that in it is seen a reflexion of the wall opposite. If the further edge of the glass be now raised, so that it is tilted a little towards one, the line of vision will also be tilted upwards, and consequently a higher part of the wall than before, or perhaps the ceiling, will be seen reflected.' In Fig. 11a the mirror is shown in * In Chapter I we have spoken of light travelling in straight lines and of its passage from a source of light or an illuminated object to the eye. We now find it convenient to trace the rays of light in
