Oldal 24 [24]
CHAPTER I
REFLEXIONS IN SMOOTH WATER
E see objects by means of the light coming
from them to the eye. They are either self¬
luminous, or, as more frequently happens, are visible
by means of borrowed light; that is to say, they are
illuminated by some external source, and from their
surfaces a portion of the light they receive radiates
in all directions. Light travels in straight lines un¬
less some obstacle divert it from its course; and the
passage of light in a straight line we call a ray.’
When a ray of light strikes a polished surface it is
bent back or veflected, continuing its course in a new
direction, and in order to understand the nature of
“reflexions” in water we must be familiar with the
law that every ray of light obeys when it falls upon
such a surface. This law states that the angle of re¬
flexion is equal to the angle of incidence; in other
words, that the ray leaves the reflecting surface at an
angle equal to that at which it falls upon it. For in¬
stance, if AB (Fig. 1) represent the surface of a plane
mirror, a ray of light falling from a point P in the
candle flame on to the mirror at C, will be reflected
towards D, the angle PCB being equal to the angle
" Ze., a beam of light of such minute transverse dimensions that
it does not materially differ from a mere line.