1. Fill in the blanks with the proper words.

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

Ans: vacuum

(b) Noise pollution is a ………. issue.

Ans: social

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

Ans: noise

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

Ans: health

2. What should we do ?

(a) The silencer of a motorcycle is broken.

Ans: 

(i) The silencer should be repaired immediately to reduce noise pollution.

(ii) Driving such a motorcycle should not be attempted until the silencer is fixed.

(b) A factory in the surroundings is producing continuous loud noise.

Ans: 

(i) We should notify the factory authorities about the loud noise.

(ii) If there are problems with machinery, they should be repaired by the factory owners.

(iii) If they do not consider and pay attention, we can lodge a complaint at the police station.

3. Write the answers in your own words.

(a) What is meant by vibration?

Ans: The rapid oscillations or to-and-fro movements of an object are called vibrations.

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

Ans: Sound is propagated in the form of waves in solids. It can be explained clearly from the below examples:

(i) 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 sound that was produced. Ask your friend to tap the table from the other end. You can hear the sound that was produced. Sound reaches your ear after travelling through the table. This implies that sound can travel as waves and through solids.

(ii) The stethoscope is another example of sound travelling through solids. Doctors use stethoscopes to listen to our heartbeat.

(c) What is meant by noise pollution?

Ans: Noise pollution is the excess of unwanted sound in the environment, which can adversely affect the health of humans and other living beings.

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

Ans: The following measures can be taken to control noise pollution:

(i) Silencers must be installed in vehicles such as motorcycles, cars, trucks, buses, and other noise-producing machines.

(ii) We should watch television and listen to music at a low volume.

(iii) Also, the use of loudspeakers as well as the horns of buses and trucks should be minimized.

(iv) Regular maintenance of automobiles should be done so that noise produced by them can be kept under check.

(v) All industrial work should be done away from residential areas.

(vi) More trees should be planted in residential areas as they help reduce noise.

4. Complete the table.