CBSE – 8th Standard Science

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Question Bank – Chapter 13 – Sound

Chapter 13

SOUND

 

Q1. How does sound travel?

Ans. Sound is Produced  by a Vibrating body, it needs a medium to travel, it can travel through any solid liquid or gas.

 

Q2. What are the properties of sound?

Ans. Sound is produced by vibrations. Amplitude and frequency are two important properties of any sound.

 

Q3. Which part of our body produces sound and how?

Ans. In humans, the sound is produced by the voice box or the larynx, voice box at the upper end of the windpipe two vocal cords, are stretched across the voice box or larynx in such a way that it leaves a narrow slit between them for the passage of air When the lungs force air through the slit, the vocal cords vibrate, producing sound.

 

Q4. What makes a sound louder or shriller?

Ans. Larger amplitude of vibration, make the sound louder. Higher frequency of vibration causes the higher pitch, and sound shriller.

 

Q5. What is the difference between noise and music?

Ans. Sound plays an important role in our life. It helps us to communicate with one another. Unpleasant sound is noise while music is pleasant sound.

 

Q6. How can human hear a voice?

Ans. The eardrum senses the vibrations of sound, It sends the signals to the brain. This process is called hearing.

 

Q7. What is frequency of a sound?

Ans. The number oscillation of per second is called the frequency. Frequency is expressed in hertz.

 

Q8. What is Oscillatory motion ?

Ans. To and fro motion of an object is known as vibration or oscillatory motion.

 

Q9. What is Noise Pollution? List some sources?

Ans. Excessive or unwanted sounds lead to noise pollution,  sounds of vehicles, explosions including bursting of crackers, machines, loudspeakers etc. at home television and transistor radio at high volumes, some kitchen appliances, desert coolers make noise.

 

Q10. Explain in what way noise pollution is harmful to humans.

Ans. Noise pollution is very harmful lack of sleep, hypertension (high blood pressure), anxiety and many more health disorders may be caused by noise pollution. A person who is exposed to a loud sound continuously may get temporary or even permanent impairment of hearing.

 

Q11. How can noise Pollution be reduced?

Ans. To reduce this pollution, silencing devices must be installed in air craft engines, transport vehicles, industrial machines and home appliances.

 

Q12. How can the noise pollution be controlled in a residential area?

Ans. The noisy operations, industries must be conducted away from any residential area.  plantation along the roads and around buildings reduces the harmful effects of noise pollution.

 

Q13. What are the sources noise pollution on our surroundings How can we reduce this?.

Ans. Use of automobile horns should be minimised. TV and music systems should be run at low volumes. Trees must be planted along the roads and around buildings to cut down on the sounds reaching the residents, thus reducing the harmful effects of noise pollution.

 

Q14. Explain during rainy season Lightning is seen earlier and thunder is heard  later?

Ans. It is caused by the difference of speed between light and sound as light is faster and speed of sound is slower thus being produced at the  same time and same distance lightning is seen earlier.

 

 

Try these :- 

Match the column :-

Animals audible range

 

  • cats                       i) 1 to 20000 Hz
  • Elephants   ii) upto 40000 Hz
  • Moths                   iii) upto 50000 Hz
  • Dogs   iv) 100 to 60000 Hz
  • Grasshoppers   v) 1000 to 240000 Hz

 

Differentiate between infrasonic, sonic and ultrasonic sounds?

Calculate distance travelled by sound in air in 15 seconds?

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