118 



LIGHT 



Examples of refraction are common. A stick thrust 

 into clear water often appears to be broken at the point 

 where it enters the water. Objects often seem irregu- 

 lar when viewed through window glass, and the size of 

 bodies may seem greater or less than 

 real when seen through a lens. In 

 such cases the changes are due only 

 to the change in direction of the light 

 rays in passing to the eye through 

 different media. 



FIG. 88 



Experiment 92. Hold a piece of thick 

 glass over a pencil so that a line from your 

 eye to the glass meets its surface at an acute angle (less than a 

 right angle). Does the pencil appear broken (Fig. 87)? Now hold 

 the glass so that the line from your eye would meet its surface at 

 right angles (Fig. 88). Does the pencil now appear to be broken ? 

 Experiment 93. Place a coin in the bottom of a dish of 

 water (Fig. 89), looking at it as from e. The rays are refracted 

 at c, so that the coin appears to be at p. Now look straight down 



FIG. 89 



FIG. 90 



upon it (Fig. 90), so that the rays pe meet the water surface at 

 right angles. Are the rays refracted? Explain the reason for 

 these results. 



137. Refraction defined From these experiments we 



see that rays travel in straight lines through each 



