Stranica 115 [115]
COLOURS IN STILL WATER 63
where it enters the water. The angle of refraction,
as explained in the note above, bears a certain de¬
finite relation to the angle of incidence. That which
at present concerns us is, however, not the relation
of these angles, but the amount of light that passes
Írom air into water compared with the amount that
is reflected at the surface; and again, the amount that
passes out of water from a point beneath the surface
compared with the amount that is reflected down
Fig. 25 (1). Fig. 25 (II).
again into the water. We shall find that the more
obliquely the ray falls on the surface, the more of it
will be reflected and therefore the less refracted, and
vice versd, the more perpendicularly it falls on the
surface, the more will enter the water and the less be
reflected.
This principle is roughly illustrated in Fig. 25 by
the relative thicknesses of the lines representing the
rays of light. For example, in Fig. 25 (1) almost the
whole of the ray AO (inclined at an angle of 40°) is
refracted along OD, only a very small fraction of the
light (about one-fiftieth) being reflected, whereas in
(II), where the ray @O strikes the surface very