CH. xx. NEWTON- DISPERSION OF LIGHT. 



167 



the wall at R ; here he put a mark. He now moved the first 

 prism, A B c, a little, so as to let the second, or orange ray, 

 pass through the hole g. This ?&y fell tipon exactly the same 

 spot of the second prism, H i K, as the red ray had done, but 

 it did not go to the same spot on the wall ; it was more bent in 

 passing through the prism, and made an orange spot at o, 



FIG. 30. 



D 



Diagram showing the Different Refraction of Rays of Different Colours. 



D E, Shutter. F, Round hole. ABC, First prism. M N, Screen receiving the 

 spectrum, g, Small hole through which the lays of only one colour can pass. 

 H I K, Second prism refracting those rays. 



above the point R. By this Newton knew that an orange 

 ray is more refracted in passing through a prism than a red 

 ray is. He moved his prism, ABC, again, so as to let the 

 yellow ray through. This was still more bent, and fell above 

 o on the point Y. In this way he let all the different 

 coloured rays pass through the hole, marking the points on 

 which they fell, and he found that each ray was more bent 

 than the last one, till he had marked out a second complete 

 spectrum on the wall. Only the two extreme rays, red and 

 violet, are traced out in Fig. 30, to avoid confusion. 



This experiment proved clearly, ist, that light is made up of 

 differently coloured rays ; and 2nd, that these rays are differently 

 refracted in passing through a prism. The red rays are least 

 bent, and the violet ones most, while each of the other rays 



