Stranica 57 [57]
REFLEXIONS IN RIPPLED WATER 31
Thus we have the well-known effect of a ripple
spreading over the water. The image of the hills
opposite, a few moments ago so vivid, becomes less
and less distinct, being interrupted by minute patches
of sky reflexion, while, as the breeze gains in strength,
it disappears altogether, and the water gleams with
light from sky or cloud. (See Plate IV.) For the
reason just given all definite reflexions in water in the
far distance vanish entirely with the commencement
of the ripple.
So far it has been assumed that only the near sides
of the waves are in view; but when the breeze is so
gentle that the height of the waves is small compared
with their length* and one is not standing too low, a
certain amount of their farther sides, as in Fig. 13 at
a, 6, c, a, e, f, is also seen.
In Fig. 11c (page 27) is shown the effect of tilting
the mirror away from us, instead of towards us, as
before; the lines of vision are now deflected delow
flexions in hundreds of minute waves, rather than a single image in
any one. For our purpose it is enough to know that light from a
given object reaches the eye after reflexion at a certain part of the
wave.
The ¢circu/ar curves (so drawn for greater convenience) represent¬
ing the wave forms in this chapter, are only rough approximations
to the theoretical wave-form, which is a so-called " harmonic curve ”
ey ay SNa
or “curve of sines.” It will be noticed that the harmonic curve is
much flatter on the sides of the waves than the circular curve.
' The “length” of a wave is the distance from one crest to the
next.