LIGHT 



123 



apparently mysterious phenomena which are produced on 

 the theater stage are caused by adjustment of mirrors. 



134. Refraction. Light is refracted (that is, bent) in 

 passing obliquely from one medium into another, as from 

 air into glass or water. It is this refraction that causes an 

 oar held partly under water to look bent at the place where 

 it leaves the water. Light from the oar 



blade is bent and therefore its direction 

 is changed when it passes from water 

 into air. The light seems to come from 

 a different position. 



The apparent change of 

 position of an object caused 

 by refraction can be shown 

 by an experiment. Put a 

 button on the flat bottom of 

 an opaque dish and place 

 yourself in such a position 

 that the top of the dish just 

 conceals the button from 

 view. Pour water into the 

 dish without moving the 

 button or yourself. The 

 button seems to rise into 



view Over the edge of the one edge of the" coin." The 'direction 



cup. This is because light of 



from the button which passed 



above your eye when the 



dish contained only air, has 



been bent away from the direction in which it started 



and has entered your eye. 



135. Refracting Bodies. Prisms and lenses are trans- 

 parent bodies which refract light. A prism has three or 

 more flat surfaces. If light passes obliquely through any 

 one of the surfaces of a prism, two effects may be produced 



FIG. 58. REPEACTION CAUSING 

 APPARENT CHANGE OF POSITION 



1. Why could not the eye receive 

 light from the coin a if the basin 

 were empty? 2. Ab and ac show the 

 direction of two rays of light from 



^f cl f ng( : d ^ st above the point 



a. Why does light seem to have come 

 from e ? 3. Through what mediums 

 does light pass from the coin to the 

 eye? 



