124 APPLIED SCIENCE 



16. Explain why a reddish lamp-shade makes a room more 

 cheerful at night. 



17. Colored lights are often seen in fireworks. What causes 

 them? 



SOUND 



1. An electric light bulb makes considerable noise when it 

 breaks. Why? 



2. How may a rotten spot in a wooden beam be detected? 



3. Why is it that persons often hold the hand behind the ear 

 that they may hear? 



4. Watch a circular saw starting through a board and notice 

 that the pitch of the buzzing tone is high. Why? 



5. Why does the pitch fall soon after the saw enters the board? 



6. Tap a steam pipe with a hammer. Can the sound be heard 

 on the floor above? 



7. If you burn gunpowder in the air it does not make a noise. 

 If the gunpowder explodes in the cannon it makes a loud noise. 

 Why? 



8. Explain how a speaking tube acts so as to make sounds 

 louder. 



9. How do we know that sound does not travel through a 

 vacuum? 



