254: 



SCIENCE OF COMMON THINGS. 



Refraction of light. 



A stick partially in water seems broken. 



Fig. 66- 



Fig 65. 



air, water, or glass, in a straight line, provided no 

 reflection occurs and there is no change of density in 

 the composition of the medium ; but when light passes 

 from one medium into another, or from one part of the 

 same medium into another part of a different density, 

 it is lent from a straight line, or refracted. 



In Fig. 66, suppose n m to represent the sur- 

 face of water, and S a ray of light striking 

 upon its surface. When this ray S O enters 

 the water, it will no longer pursue a straight 

 course, but will be refracted, or bent towards 

 the perpendicular line, A B, as in the case of S 

 H. The denser the water, or other fluid, may 

 be, the more the ray S O H will be refracted, or 

 turned towards A B. 

 167O Does air possess the property of refracting light f 



Yes ; the more dense the air, the greater is its refrac- 

 tive power. 



167 f 1 Why does the part of a stick immersed in the water appear lent 

 or broken ? 



The water and the air being of different densities, 

 the rays of light proceeding from the part of the stick 

 contained in the water are refracted, or caused to deviate 

 from a straight line as they pass from the water into 

 i the air ; consequently that portion of the 

 [stick immersed in the water will appear 

 to be lifted up, or to be lent in such a 

 manner as to form an angle with the part 

 | out of the water. 



The bent appearance of the stick in water is repre- 

 || sented in Fig. 67. For the same reason, a spoon in a 

 glass of water, or an oar partially immersed in water, 

 always appears beut. 



