QUESTIONS 365 



by means of which many of the substances in the sun have 

 been detected. 



Changing conditions of the atmosphere affect the colors 

 of sunlight in various ways. Rainbows, halos, coronas, 

 and mirages are owing to peculiar conditions of the atmos- 

 phere, through which light is coming to the eye. 



Natural and artificial lighting of houses deserves the most 

 careful consideration, for the sake of convenience, comfort, 

 and health. 



QUESTIONS 



What experiences have you had which cause you to think that 

 light travels in a straight line? 



If a boy is reading two feet from a light and moves to a distance 

 of eight feet, how much ought the strength of the light to be in- 

 creased to enable him to read with the same ease? 



How long does it take light to come from the sun to the earth ? 



What experiences have you ever had which illustrate refraction ? 



Why do not colors look the same in artificial light as they do in 

 sunlight ? 



How would you arrange the windows, hangings, and artificial 

 lights of a room to make it most healthful and cheerful? 



