SPHERICAL REFLECTORS. 
those through which the object is moved. In fine, when the 
object approaches to F, the image will recede indefinitely behind 
the reflector, and will disappear altogether when the object 
actually arrives at f. 
All these phenomena admit of easy verification, by placing a 
candle in the several positions here assigned, and observing its 
image reflected in the mirror. 
13. If the reflector be convex, the object L M (fig. 8), will have 
its image at the points l m, between the reflector and the 
principal focus F. 
The rays pro- Fig. 8. 
ceeding from the 
several points of 
the object L M 
will, after re¬ 
flection, diverge 
as if they had 
proceeded from 
the corresponding points of l m, and will produce upon the vision 
the same effects as if an object had been actually placed at l m . 
The image in this case, therefore, will be erect, and it will 
be less than the object in the proportion of o l to o L. In this 
manner is explained the effect familiar to every one, that convex 
reflectors exhibit a diminished picture of the object placed before 
them. 
14. IMAGES PRODUCED BY TRANSPARENT BODIES. 
Fig. 9. 
When light enters or issues from a transparent body its direction 
is deranged, its rays appearing to be broken at the points where 
they pass through the surface of 
the body. This effect is called 
refraction. 
15. Thus, if the line A b (fig. 
9) be supposed to represent the 
surface of such a body, and that 
a ray, E I, enter it at I, this ray, 
instead of preserving its direc¬ 
tion, will be broken, as it were 
at i, and will take the direction 
I R, If the ray has been transmitted from R to I, it would, on 
issuing from the surface A b at I, have been broken, and would 
take the direction i E. 
Let the line n n' be drawn perpendicularly to the surface A b. 
If the ray E I be supposed to enter the surface at I, it will be 
always refracted towards the perpendicular I n'. 
x\ 
A \ 
r ’ 
N' 
V 
89 
