96 SCIENTIFIC RECREATIONS. 



metrical centre and the focus, the image will appear to be in front of 

 the mirror. 



We can understand these phenomena by the accompanying diagrams. 

 Suppose a ray A;z passes from one object, AB, at right angles, it will be 

 reflected as n A C, the ray A C being reflected to F. These cannot meet in 

 front of the mirror, but they will if produced meet at a, and the point A will 

 be reflected there ; similarly B will be reflected at b y and thus a magnified 



Fig. 87. Reflection of mirrors (I). 



Image will appear behind or at the back of the mirror's surface. In the next 

 diagram the second supposed case will produce the image in the air at 

 ab, and if a sheet of paper be held so that the rays are intercepted, the 

 image will be visible on the sheet. In this case the perpendicular ray, Afc, 

 is reflected in the same direction, and the ray, ac, parallel with the axis is 

 reflected to the focus. These rays meet at a and corresponding rays at b y 

 when the image will be reproduced ; viz., in front of the mirror. 



Fig. 88. Reflection of mirrors (II). 



The concave mirror is used in the manufacture of telescopes, which, 

 with other optical instruments, will be described in their proper places. We 

 will now look at the Refraction of light 



Bodies which permit rays of light to pass through them are termed 

 transparent. Some possess this property more than others, and so long as 

 the light passes through the same medium the direction will remain the 

 same. But if a ray fall upon a body of a different degree f density it 

 cannot proceed in the same direction, and it will be broken or refracted, 

 the angle it makes being termed the angle of refraction. 



