PHENOMENA OF LIGHT 



111 



perpendicular lines (normals) appear to pass with reference 

 to the images of the 2-inch and 4-inch marks. 



8. Draw a line on a sheet of paper to represent a mirror 

 surface, and in front of it a 3-inch arrow oblique to this line. 

 Having in mind what is suggested in paragraph 7, locate 

 the image of this arrow on the other side of the mirror line 

 by use of ruler and protractor. 



COLOR PHENOMENA 



Note carefully the procedure as the teacher follows out the direc- 

 tions given below. Be ready to state the results obtained, and the 

 significance of them as called for in turn. 



1. So adjust a triangular glass prism in a beam of sun- 

 light as to get a solar spectrum on a white wall of the room 

 (or other screen) . 

 Then darken the 

 room. By use of 

 a strip of card put 

 over the prism 

 faces, determine 

 (a) through which 

 face the incident 

 light enters; 

 (6) through which 

 the light emerges. 

 Call the edge formed 

 by the intersection 

 of these faces the 

 refracting angle of 



the prism, and the side opposite it the "base" of the prism. 

 Note (a) whether the change in direction of the incident 



N 



FIG. 78. Dispersion of light, and the solar 

 spectrum. 



