178 LABORATORY LESSONS IN GENERAL SCIENCE 



rays is toward the base, or away from it ; (6) which of the 

 colors of the spectrum is bent farthest around, and which 

 least. Name these colors of the solar spectrum in order, 

 beginning with the red. 



A spectrum, whatever the source of light, is defined as 

 an arrangement of colors in the order of their refrangibility, i.e., 

 according to the degree they are bent from a straight line 

 by refraction. Refraction of light by definition is a bending 

 of the rays, i.e., a change in the direction of light, by reason 

 of changes in the density of medium. (As from air into 

 glass, and then from glass into air.) 



2. Using a sheet of writing paper that has been dipped 

 into hot melted paraffine to make it translucent, trace the 

 emergent rays outward from the prism and note (a) what 

 their relative direction is after refraction ; (b) why it is that 

 refraction commonly occurs without noticeable dispersion. 



3. Let some one on the far side of the room look through 

 a long narrow opening in a cardboard held for him in the 

 different color parts of the spectrum in turn, and tell in each 

 case what the color sensation is. 



4. Let the spectrum fall upon a plane mirror, and note 

 (a) what is done to the light waves giving the spectrum col- 

 ors ; (6) whether there has been any change in the relative 

 positions of these colors. Explain how it is that all of 

 these different colors (light waves) come to every one of 

 you, although you are seated in different parts of the room. 



5. Hold a narrow strip of blue cardboard (as pure blue 

 as obtainable) in different parts of the spectrum, and note 

 its changes in appearance. It is explained that any pigment 

 (the material upon which the color of a body depends) re- 



