USES OF REFRACTION 



2S3 



is called the angle of incidence. The angle POS is called the 

 angle of refraction. 



The angle of refraction is the angle formed by the refracted 

 ray and the perpendicular at the 

 point where the light strikes the 

 surface. 



When light passes from air into 

 water or glass, the refracted ray is 

 bent toward the perpendicular, so 

 that the angle of refraction is 

 smaller than the angle of inci- S P 



dence. When a ray of light passes FIG. 124. When the ray RO enters 

 r i i the water, its path changes to OS. 



from water or glass into air, the 



refracted ray is bent away from the perpendicular so that the 



angle of refraction is greater than the angle of incidence. 



The bending or deviation of light in its passage from one 

 subject to another is called refraction. 



Uses of refraction. If it were not for refraction, or the 

 deviation of light in its passage from medium to medium, 

 the wonders and beauties of the magic lantern and the camera 

 would be unknown to us; sun, moon, and stars could not be 

 made to yield up their distant secrets to us in photographs ; the 

 comfort and help of spectacles would be lacking, spectacles 

 which have helped unfold to many the rare beauties of nature, 

 such as a clear view of clouds and sunset, of humming bee and 

 flying bird. Books with their wealth of entertainment and 



1 information would be sealed to a large part of mankind, if glasses 

 did not assist weak eyes. 



By refraction the magnifying glass reveals objects hidden 

 because of their minuteness, and enlarges for our careful con- 

 templation objects otherwise barely visible. The watchmaker, 



! unassisted by the magnifying glass, could not detect the tiny 

 grains of dust or sand that clog the delicate wheels of our 



