102 INTRODUCTION TO GENERAL SCIENCE 



are equidistant from a given point lie on the arc of a circle. 

 That is why a rainbow is curved. 



References : 



1. 1103 : 174-175. The Rainbow. 



2. 1803 : 452-454. The Rainbow. 



a. 1801 : 232-235. The Rainbow and its Cause. 



b. 1802 : 254. The Rainbow. 



c. 1804:370-371. The Rainbow. 



d. 1805 : 241-244. The Rainbow and its Cause. 



e. 1807 : 335-337. The Rainbow. 

 /. 1808 : 415-418. The Rainbow. 



g. 1809:324-325. Action of a Raindrop on Sunlight, the 

 Rainbow. 



Experiment 37. The Rainbow. 



Apparatus : Piece of glass 3" X 3", medicine dropper. 



Materials : Lubricating oil. 



a. Rub a very little lubricating oil on one surface of the 

 glass plate and place a drop of water on it, using the medicine 

 dropper. The drop must be small enough to be nearly spheri- 

 cal. Place the plate in the sun and move the head until, in 

 one position or another, all the colors of the rainbow have 

 been seen. Why is the oil used ? Why should a small drop 

 be used ? 



74. DIFFUSION OF LIGHT 



A mirror reflects light in a regular way. This is true of 

 any smooth and bright surface. Rough bodies reflect light 

 in an irregular manner, and we see no reflection as such, 

 but we see the object which reflects the light. This is called 

 diffused reflection. 



Light is diffused to a very great extent by particles* of dust 

 in the air which are too small to be seen. We obtain the light 



