26 
PHYSICS. i 
now be stated thus—The incident ray, the normal, and the reflected ray 

Fig. 25. 
are all in one plane. Again, ede is called the angle 
of incidence, and cdb the angle of reflection ; and 
the second law of reflection is—The angle of reflec- 
tion 1s equal to the angle of incidence. Two other 
facts will now be easily understood. 
1. Rays of light that fall on a reflecting surface 
parallel to each, will be reflected parallel to each 
other. Rays being reflected from a surface at the 
same angle as they fall upon it, it is evident that 
after reflection they must remain parallel. If P and 
Q (fig. 25) are parallel when they fall on CD, R and 8 will also be parallel. 
2. When divergent rays, or rays that spread out from a point, fall 

Fig. 26. 
on a mirror, the point from which ‘the 
reflected rays seem to proceed, is on the 
opposite side of the mirror, and at a 
¢ distance equal to the distance of the 
= = point from which the rays. actually pro- 
ceed. Thus, let rays, diverging from 
the point Q (fig. 26), fall on a mirror at 
A and B, and be reflected in the direction 
of R and 8; the point gq, from which 
they seem to proceed, is on the opposite 
side of the mirror, and the distance Ng is equal to the distance NQ. 
Refraction. 
The body or substance through which light passes is called a medium. 
When light passes from one medium into another, it is refracted or 
bent out of its straight course. This is seen by a very simple 
‘oo. 

Fig. 27. ~ into the air, so that the light . 
experiment. Let a coin be placed 
in the bottom of a basin so 
that it is just out of sight. If 
without moving the coin, it will 
gradually come into sight, the 
cause being, that the light from 
the coin is bent out of the straight 
line in passing from the water 


that comes from a, along aDC, 
seems to come straight from 6, and the coin seems to be raised up. 
1 From Latin dis, asunder, and vergo, to incline, 
water be poured into the basin . 
Se 
