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8 LIGHT AND WATER
over the horizontal mirror (Fig. 3), the image of any
point A on the base of the object will appear—no
matter what the position of the observer—at a, as far
below the surface of the mirror in a vertical line as
the point A itself is above it (the perpendicular line
Aa being bisected by the surface of the mirror at O) ;
in the same way the image of B will appear at 4, that
E
Fig. 3. The reflexion is a new view of the object reflected.
of C will appear at c, and so on for every other point;
so that we get an inverted image adc, in which every
part of the object is exactly reproduced. The image
thus formed is called a vzvtual image, because, though
it has no actual existence, the effect on the eye is
exactly the same as if it were a real object. If the
right hand is held up to a looking-glass a left hand
appears on the other side; so we may say that the
image is related to the object reflected in the same
way that the left hand is related to the right. The