452 



.CONVEX MIRRORS. 



mirror and its centre of curvature. The point / is 

 called the principal .focus of the convex mirror, being 

 in this case, however, not a real focus as in the case of 

 concave mirrors, but a principal virtual focus; its 

 distance from the mirror is the focal length of the latter. 

 As in the case of concave mirrors, the place, position 

 and magnitude of images produced by convex mirrors 

 may be found by drawing from each of the extreme 

 points of an object, straight lines representing rays of 

 light proceeding from these points, and 'tracing the path 

 after reflection of two such rays, one being drawn to 

 the centre of curvature, the other parallel to the axis. 

 The ray A d, fig*- 256, drawn from A to the centre of 



FIG. 256. 



curvature c, is reflected upon itself, that is, in the 

 direction d A ; the ray A e, which proceeds from A 

 parallel to the axis, is reflected so as apparently to 

 proceed from/, that is, in the direction eg. Both rays, 

 like all the others which emanate from J., take after 

 reflection a direction as if proceeding from the point a: 



