16, 



THE OCEAN OF AIR 



11. Refer to the diagram in Experiment 9. From the fol- 

 lowing statements choose the ones which may be causes 

 of the cork's going to the bottom of the dish. 



(a) The water pressure was greater than the air pres- 

 sure. 



(b) The air pressure was greater than the water pres- 

 sure. 



(c) The cork will not float in air. 



(d) Air and water can not occupy the same space at 

 the same time. 



12. Compressed air makes possible many of our athletic 

 games such as basketball, football, soccer, and tennis. Ex- 

 plain how this is true. 



TOPIC 4. THE RELATION OF AIR TO SOUND 



SUGGESTED PROBLEMS AND QUESTIONS 



1. How does sound affect our daily lives? 



2. What is sound and how does it travel? 



3. What is the nature of musical tones? 



4. How is the human ear constructed for hear- 

 ing? 



5. How may different tones be produced on 

 musical instruments? 



How does the phonograph reproduce sound? 



SUGGESTIONS AND HELPS FOR STUDY 

 1. Try to find the answers to the following ques- 

 tions in solving the problems above. Some can be an- 

 swered by the experiments, others by the reference 

 readings. 



a. Answer these questions about problems 1, 2, 

 and 3. 



1) In what ways may sound be produced? 



2) How fast does sound travel? 



3) Does it travel through all substances? 



This may be answered when you have performed 

 Experiment 11. 



4) What makes a siren screech? 



5) What is the difference between a noise and a 

 musical tone? 



b. Answer these questions to solve problem 4 

 above. 



1) What are the parts of the human ear? 



2) What is the duty of each part in producing the 

 sensation of sound? 



3) What are the causes of deafness ? 



4) What are the highest and lowest numbers of 

 vibrations which can be heard by the human ear? See 

 Experiment 12. 



c. Answer these questions about problems 5 and 

 6 above. 



1) How are phonograph records made? 



2) What difference is noticed when a phonograph 

 record runs slowly and when it runs fast? This may be 

 answered by experiment. 



3) How does a phonograph record appear when 

 looked at under a magnifying glass? 



4) How is a phonograph constructed? 



5) How are different tones produced on a violin 

 or other stringed instrument? 



6) How are different tones produced on a trombone 

 or other wind instrument? Experiment. 



2. You may find the following new words and 



phr?ses in this study: 



compression the pushing or squeezing together of a 

 substance. 



diaphragm a thin membrane or disk which may vi- 

 brate. 



pitch Two musical tones are said to have difference 

 of pitch if they differ in the number of vibrations 

 made per second. A low or bass tone has few vibra- 

 tions per second and hence a low pitch. A high or 

 soprano tone has a greater- number of vibrations per 

 second and a higher pitch. 



quality The quality of a musical tone enables one to 

 tell a difference between the same tone sounded on 

 a piano and a cornet. 



vibration a movement to and fro as one vibration of a 

 violin string. 



EXPERIMENTS OR DEMONSTRATIONS WHICH WILL 

 HELP ANSWER THE PROBLEM QUESTIONS 



Experiment 10. How may sound be produced and 

 what causes it? 



Vibrate rods of metal held in a clamp or vise by stroking 

 with a cloth dipped in rosin. Vibrate air columns in bottles 

 and flasks by blowing across them. Vibrate strings. Strike a 

 tuning fork on a rubber stopper and touch the tines to water 

 in a glass. Place little paper riders on a stretched violin 

 string and pluck it. 



Record the notes and results of this experiment in your 

 notebook. 1 



Experiment 11. What substances transmit sound? 



Use a tuning fork as a sounding body and transmit its 

 sound to a blackboard, door, or table top through as many 

 different substances as you can. The following are suggested : 

 wood, cardboard, felt, string, wire, iron rod, brass rod, water, 

 wood alcohol. In the case of liquids paste a disk of wood or 

 cardboard to the bottom end of the tuning fork and rest this 

 against the surface of the liquid in a glass. 



In your notebook 2 record the results of this experiment 

 and list the substances which you found to transmit waves. 



1 See accompanying workbook, p. 8. 



2 See accompanying workbook, p. 8. 



