HOW DO I USE LIGHT? 133 



many places the use of an orange light for pedestrians to 

 pass while auto traffic remains at rest is a very helpful 

 aid to safety. Our use of colored lights and following the 

 messages they bring to us make possible the rapid clearing 

 of traffic jams and greater freedom from accidents. 



SELF-TESTING EXERCISE 



Select from the following list those words which best fill the blank spaces 

 in the sentences below and arrange the words in proper numerical order. 

 A word may be used more than once. 



radiation radiant orange 



chemical mechanical red 



electricity image blue 



lights cross inverted 



heat green object 



colored straight light 



Light is a form of (1) energy just as (2) and (3) 



are. (4) is used whenever we read or see an object. Since 



light travels in (5) lines, whenever light from an object passes 



through a small opening, the rays (6) and produce an (7) 



image. When (8) signal (9) are used, it is common to 



use (10) for danger and (11) for safety. 



STORY TEST 



FLORENCE WRITES AN ESSAY ON LIGHT 



Read carefully and critically. List all the errors and suggest cor- 

 rections. 



There are two kinds of light, black and white. This has been 

 proven by pictures taken of lightning. Some streaks are black 

 and are produced by black lightning. We cannot see objects by 

 black light ; we use the white light. If a candle is behind a block 

 of wood, we cannot see it because light travels in straight lines. 

 If light radiates from a red hot iron, the light goes in all directions 

 and then may go around corners, in curved lines. If light rays 

 from two objects were to meet, they would destroy each other, and 

 where they come together, the two bodies would be invisible. 

 The reason automobiles have red headlights is because it is danger- 

 ous to be in front of a car. The green tail light indicates safety. 



