LIGHT. 393 



N. B. These 8 colours, by combination, make seven. 

 1. BED. 2. Eed and yellow form ORANGE. 3. YEL- 

 LOW. 4. Yellow and blue make GBEEN. 5. BLUE. 

 6 and 7. Shades of blue called INDIGO and VIOLET. 



Q. How is it KNOWN, that a ray of light 

 consists of several different colours ? 



A. Because, if a ray of light be cast 

 upon a triangular piece of glass (called 

 a prism), it will be distinctly divided into 

 seven colours: 1. Red; 2. Orange; 

 3. Yellow ; 4. Green ; 5. Blue ; 

 6. Indigo; and 7. Violet. 



Q. Why does a PEISM DIVIDE a ray of light 

 into VABIOTJS COLOURS ? 



A. Because all these colours have 

 different refractive powers. Red is 

 refracted least, and blue the most ; there- 

 fore, the blue colour of the ray will be 

 bent to the top of the prism, and the red 

 will remain at the bottom. 



Here the ray A B received on a prism, would have the 

 blue part bent up to C; the yellow part to D ; and the 

 red part no further than E. 



