SOUND

Question 1: Fill in the blanks with the proper words. 

(a) The propagation of sound does not occur through a ........... . 

(b) Noise pollution is a .......... issue. 

(c) The sound which is disagreeable to the ears is called..... .

 (d) Noise has adverse effects on our .......... .

ANSWER: (a) The propagation of sound does not occur through a vacuum.

(b) Noise pollution is a social issue.

(c) The sound which is disagreeable to the ears is called noise.

 (d) Noise has adverse effects on our health.

 Page No 96: 

Question 2: 

What should we do ?

 (a) The silencer of a motorcycle is broken. (b) A factory in the surroundings is producing continuous loud noise.

 ANSWER: 

a) If the silencer of a motorcycle is broken, then take the motorcycle to a mechanic and get it reinstalled or repaired.

 (b) If a factory in the surroundings is producing continuous loud noise, then we can lodge a complaint against the factory to a local government body citing the troubles faced by the residents around and the danger it is causing to the environment.

 Page No 96:

 Question 3:

 Write the answers in your own words.

 (a) What is meant by vibration ?

 (b) Explain with the help of practical examples how sound is propagated through solids.

 (c) What is meant by noise pollution? 

(d) What measures will you take to control noise pollution ? 

 ANSWER: (a) The to and fro motion of a body about its mean position is known as vibration.

 (b) Sound is propagated in the form of waves in solids. It can be explained clearly from the below examples: Place your ear on one end of a long table. Ask your friend to tap the table from the other end. You can hear the produced sound. Sound reaches your ear after travelling through the table. This indicates that sound can travel through solids and in the form of waves. ​Stethoscope is another example of sound travelling through solids. Doctors use stethoscopes to listen to our heartbeat.

 (c) Noise pollution is the excess of unwanted sound in the environment. It can adversely affect human and other living beings health.

 (d) Following measures can be taken to control noise pollution: To control noise pollution, we must control its source. Hence, silencers must be installed in vehicles such as motorcycles, cars, trucks, buses, and other noise producing machines. We should watch television and listen to music at a low volume. Also, use of loudspeakers as well as horns of buses and trucks should be minimized. Regular maintenance of automobiles should be done so that noise produced by them can be kept under check. All industrial work should be done away from residential areas. More trees should be planted in residential areas as they help in reducing noise.