162 



HOW WE USE LIGHT 



candle burning and jar empty at the start. Pour water slowly 

 into the jar. Your audience expects the candle to burn until the 



water reaches the wick, 

 but it continues to burn 

 until they see the water 

 well above the top of 

 the flame. If the jar of 

 water is shown by re- 

 flection, hold the candle 

 where the audience can 

 see it. Have the match 

 ready. Have the cur- 

 tain closed while you 

 " place the candle in the 

 jar of water and light it." 

 You have the proper spot 

 marked on the table 

 where you place the 

 candle. After lighting 

 it, have the curtain 

 drawn aside and the 

 audience sees the candle 

 burning in the jar of 

 water. Test the posi- 

 tions before the audience 

 arrives. 



4. MAKE A PINHOLE CAMERA AND TAKE A PHOTOGRAPH WITH IT 



A small prize may be offered for the best picture made by a 

 member of the club. A pinhole camera may be made in the follow- 

 ing way. Use a box about five inches square and three inches deep. 

 It must have a cover which slides down over the box for a depth of 

 at least one inch. The interior must be painted black and made 

 light-tight. Cut a hole one half inch in diameter in the middle of 

 one side or end of the box. Paste a piece of tinfoil on the inside of 

 the box over the hole. Make a pinhole in the center of this tinfoil. 

 The success of your picture depends on the care with which you 

 make this hole. The best results are obtained when the diameter of 

 the pinhole is in proportion to the square root of the distance from 

 the pinhole to the plate. 1 



1 Use the following formula : 



Diameter of pinhole = # ^Distance of plate from pinhole 



K = .0008 

 This diameter may be measured by some machinist or science in- 



