Oldal 49 [49]
CHAPTER II
REFLEXIONS IN RIPPLED WATER
HE absolutely smooth surface thus far assumed,
giving a perfect, but lifeless, reflexion of neigh¬
bouring 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 illus¬
trate 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