358 THE SUN'S GIFT OF LIGHT 



absorbed its energy is changed into heat energy or chemical 

 energy. 



Experiment 107. Obtain pieces of cloth of a number of different 

 colors. Darken the room and light a Bunsen burner. Adjust 

 the holes at the bottom so that it will give but little light. Dip a 

 glass rod in a solution of common salt and place it in the flame of 

 the burner. The flame will be colored a brilliant yellow. Now 

 examine the colors of the different pieces of cloth. Do they appear 

 as they did in sunlight? 



The color of a non-luminous substance is due to the kind 

 of light it transmits or reflects. If a colored object is looked 

 at by lamplight it will not appear of the same color as by 

 sunlight because the lamplight is deficient in some of the 

 colors of sunlight. Therefore the object cannot reflect the 

 same combination of colors when exposed to lamplight 

 that it reflects when exposed to sunlight. 



If, for example, an artificial light lacks red rays, then 

 a red surface exposed to it would absorb all the colors of 

 the light and would appear black because there are no red 

 rays to be reflected. 



By combining the prism with the telescope, scientists 

 have an instrument for examining the spectrum of the sun. 

 With this instrument the spectrum is found to be crossed 

 by hundreds of fine black lines scattered along the band of 

 color. By bringing known elements to a white hot vapor 

 and comparing their spectra with the spectrum of the sun, 

 scientists have determined many substances that are in the 

 sun. 



Sunlight is affected by the air through which it comes. 

 When the sun sets at night and the rays come to us through 

 a great thickness of murky air which is near the surface of 

 the earth, the light often appears red or yellow. The heavy 



