RADIATION 93 



time the twelve rays are distributed over that part of the earth 

 represented by AB, but in the winter the same number of rays are 

 distributed over CD. Fig. 72. 



At midday the rays of the sun are more vertical than in the 

 morning and afternoon; hence, we get the greatest amount of heat 

 at that time. 



QUESTIONS 



1. Why are thermos bottles shiny? 



2. Why should radiators be dark and rough? 



3. Why do soldiers wear white uniforms in the tropics? 



4. Why are the streets of a city, or the stone walls of a quarry, 

 warmer than the open country? 



5. Why will snow melt faster under black cloth than under white? 



6. Why wear white during the summer months, and black dur- 

 ing the winter months? 



7. Which would be the coolest in summer, white, tan, or black 

 shoes? Why? 



8. What would be the difference between trying to keep water 

 warm in a glass bottle and in a shiny aluminum bottle? 



9. Why does snow covered with dirt melt much faster than new 

 snow? 



10. Why are ashes helpful on ice? 



11. What would be the difference in the amount of heat received 

 by us if the sun were the color of the blue flame of a Bunsen burner? 



12. Why doesn't the earth get heated just as much by radiation 

 on a cloudy day? 



13. Why is water warmer in the evening than the adjacent land? 



14. When will you get the greater sunburn when the sea is 

 rough or smooth? Why? 



15. Why will frost appear more quickly on a clear night? 



16. Why will dark soils absorb heat more rapidly than light- 

 colored soils? 



17. Why will the bare earth become heated more quickly than 

 earth covered with vegetation? 



18. Why doesn't the frost in central Alaska, which often extends 

 175 feet down in the earth, go out during the summer? 



