22 LIGHT 



12. Other Changes of Color which are Caused by the 



Sunlight. 



If we are out in the sunlight a great deal our skin 

 becomes brown and we say that we are tanned. This 

 change of color is due to the sun and it takes place in 

 order to protect the body from the effects of too much 

 sunlight. Some persons do not tan very easily, but be- 

 come red and often blisters are caused where the skin has 

 been exposed very long to the sunshine. Even persons 

 who do tan easily are sunburned if they try to become 

 tanned in a few days, while if they are not too long in 

 the sunlight at one time, the skin will protect itself by 

 putting a shield between the sun and the tender inner 

 skin. Just as smoked glass shut out so much sunlight 

 that we could look at the bright noonday sun without 

 hurting our eyes, so the tanned skin keeps out the strong 

 sunlight and we can expose it to the sun's glare without 

 harm. If the coloring material is not distributed evenly 

 throughout the skin little patches come which are called 

 freckles. 



When we speak of the sun as causing plants to be 

 green and the skin to tan, we must remember that the 

 plants and the skin are alive. If the sun shines upon 

 things which are without life it can affect the color which 

 the things have, causing it to become lighter, and in some 

 cases, even making the material white or nearly white. 

 The change in color is called fading, while the removal of 

 the color from an object is called bleaching. 



Experiment 13: Fading and Bleaching, 

 a. Obtain several pieces of differently-colored cot- 

 ton cloth and cut each piece into halves. Keep one of 



