Important Questions for CBSE Class 8 Science Chapter 13 - Sound

Very Short Answer Questions:

1. Which one the following acts as a medium for propagation of sound.

A. Solid

B. Gas 

C. Liquid 

D. All of These

Ans: D. All of these act as a medium for propagation of sound.

2. The range of audible sound for a human being is ____________. 

A. 20 Hz to 20,000 Hz 

B. 20 Hz to 10,000 Hz 

C. 10 Hz to 10,000 Hz

D. 20 Hz to 40,000 Hz

Ans: A. 20 Hz to 20,000 Hz is the range of audible sound for a human being.

3. The loudness of sound depends upon ______________. 

A. Amplitude 

B. Frequency

C. Time Period

D. Speed

Ans:A. amplitude is the property on which loudness of the sound depends upon.

4. Which one of the following will have long vocal cords? 

A. Women 

B. Men

C. Children 

D. None of the above

Ans: B. Men have long vocal cords

5. Shrillness of a sound is determined by___________________ of vibration.

A. Amplitude 

B. Frequency 

C. Time Period 

D. Speed

Ans: B. Frequency of vibration determines the shrillness of a sound.

6. Which one of the following instruments produces sound through vibrations? 

A. Ghatam 

B. Tabla

C. Flute 

D. Sitar

Ans: D. Sitar is the instrument which produces sound through vibration.

Very Short Answer Questions:

7. To and fro motion of an object is called _____________. 

Ans: Vibration is the to and fro motion of an object.

8. Define frequency? 

Ans: Frequency is the number of oscillations made per second. 

9. What is the unit of frequency? 

Ans: Hertz is a unit of measurement for frequency. The sign for it is Hz.

10. _______ and _______ are two important properties of any sound. 

Ans: Amplitude and frequency are two important properties of any sound.

11. In humans, sound is produced by the ______________. 

Ans: in humans, sound is produced by the Voice box or larynx 

12. For the human ear, the range of audible frequencies is roughly from ______ to ______ Hz. 

Ans: 20 to 20,000 is the range of audible sound for the human ear.

13 Define noise. 

Ans: Noise is the name given to unpleasant sounds.

14. Give two examples of noise pollution.

Ans: During an event, the use of crackers and loudspeakers.

15. What would be the sound produced in a bus station or railway station called as? 

Ans: Unpleasant noise will be produced in both locations, which is known as noise.

16. Sound cannot travel through a _____________. 

Ans: Sound cannot travel through a vacuum.

Short Answers Questions:

17. Briefly describe the loudness of sound. 

Ans: The Square of the amplitude of the vibration producing the sound determines the loudness of the sound. For example, doubling the amplitude increases the loudness by a factor of four. The decibel is a measurement of how loud something is (dB).

18. Classify the following into music and noise. Desert coolers, sound produced by harmonium, string of sitar, television and transistor radio at high volumes

Ans:

19.  Describe oscillatory motion. 

Ans: Oscillating is the process of swinging back and forth in a continuous motion, and oscillating motion is the result of that process.

20.  Label the parts of the human ear in the below given picture.

Ans: A. Inner ear, B. Eardrum

21.  Correct the following statements. 

a. Noise is one which is pleasing to the ear. 

Ans: Musical sound is one which is pleasing to the ear

22. Sounds of frequencies more than 20 Hz but less than 20,000 Hz cannot be detected by the human ear. 

Ans: Sounds of frequencies more than 20 Hz but less than 20,000 Hz can be detected by the human ear.

23.  Explain with an activity that sound travels in liquids. 

Ans: Fill a bucket with water and, using one hand, shake a bell under the water, making sure the bell does not touch the bucket's body. Now carefully place your ear on the water's surface; you will hear the ringing bell, proving that sound can travel through water.

24. Give an example to show that the frequency determines the shrillness or pitch of a sound. 

Ans: A low-frequency vibration is produced by a drum. As a result, it makes a low-pitched sound. A whistle, on the other hand, has a high frequency and hence generates a higher pitch sound.

25. It is said that “The loudness of sound depends on its amplitude”. What happens to the sound when the amplitude of vibration is large and vice versa?

Ans: Because the loudness of sound is determined by its amplitude, so  the sound produced is loud when the amplitude of vibration is significant. The sound generated is weak when the amplitude is tiny.

26. Sound plays an important role in our life. Why? 

Ans: Sound is crucial because it enables us to communicate with one another.

27. Identify the type of frequency in the below given pictures.

Ans:

 a. High frequency 

 b. low Frequency

Long Answers Questions:

28. Explain how sound is produced in human beings. 

Ans: The voice box or the larynx in humans produces the sound. The larynx is located near the top of the windpipe. Two vocal cords are stretched across the voice box or larynx in such a way that a thin slit for air passage is left between them. The vocal cords vibrate when the lungs force air through the slit, producing sound. The muscles that link to the voice cords can tighten or loosen them. The sort or quality of voice produced when the vocal cords are tight and thin differs from that produced when they are loose and thick.

29. Demonstrate an activity to show that sound needs a medium for propagation 

Ans: Take a tumbler, either metal or glass. Make sure it's completely dry. Put a cell phone in there. Request that a friend call this cell phone from another cell phone. Pay close attention to the ring. Now, wrap your hands over the tumbler's rim. Place your mouth in the space created by your hands. Tell your friend to ring the phone once more. While sucking air from the tumbler, listen to the ring. Keep an eye on the tumbler and take it out of your mouth. It's probable that the decreased volume of air in the tumbler contributed to the ring's decreased volume. There would be no sound if the tumbler is completely devoid of air. This demonstrates that sound requires a medium in order to travel.

30. List the harmful effect of Noise pollution

Ans: Excessive noise in the environment can lead to a variety of health issues. 

a. Lack of sleep, 

b. Hypertension (high blood pressure), 

c. Anxiety, 

d. A person who is continuously exposed to a loud sound may suffer from temporary or permanent hearing loss.

31. How can we control Noise pollution?

Ans: We must control the causes of noise pollution in order to reduce noise pollution. 

a. Aircraft engines, transport vehicles, industrial machines, and household appliances must all have noise-cancelling devices fitted. 

b. All loud operations must take place outside of any residential areas. Industries that produce noise should be located distant from such regions.

c. Automobile horns should be used sparingly. Low-volume television and music systems are recommended.

d. Trees should be planted along highways and around buildings to reduce the amount of noise that reaches households, hence lowering the negative impacts of noise pollution.

CBSE Important Questions Class 8 Science Chapter 13

Solved Questions from Sound Chapter Class 8 Questions

1. Explain how sound is produced in human beings.

Answer: The voice box or the larynx produces the sound in human beings. The larynx is at the upper end of the windpipe. A narrow slit is left between the two vocal cords because they are stretched over the larynx. This helps in the passage of air. The lungs force air through the slit, producing sound as the voice box vibrates. Muscles that are attached to the vocal cords make the cords tight or loose. When the vocal cords are flexible and thick, the type or quality of voice is different from that of when they are tight and thin.

2. Explain an activity to show that sound needs a medium to propagate.

Answer: Take a metal or glass tumbler, making sure that it is dry. Place a cell phone in it and ask a friend to ring that phone with another cell phone. Now carefully listen to the ring. Now surround the rim of the tumbler with your hands. After this, put your mouth on the opening between your hands. Now ask your friend to call the cell phone again. Listen to the ring while sucking air from the tumbler. Observe and remove the tumbler from your mouth. It is possible that the decreasing amount of air in the tumbler had something to do with the decreasing loudness of the ring. If the air is sucked completely from the tumbler, you will not hear any sound. This is how we can prove that sound needs a medium to propagate.

3. How can we control noise pollution?

Answer: We can control noise pollution by controlling the sources of noise. Following are some of the ways we can control noise pollution:

1. Silencing devices should be used in aircraft engines, industrial machines, transport vehicles, and home appliances.

2. All noisy activities should be conducted far away from residential areas. Industries should be set up away from residential areas because of how much noise they produce.

3. The use of TV, music systems, and automobile horns should be minimised. 

4. More trees should be planted to curb the harmful effects of noise pollution.

4. Describe the oscillatory motion.

Answer: Oscillation is the process of swinging to and fro in an uninterrupted manner and oscillation motion is the movement created by this process.

5. What are some of the harmful effects of noise pollution?

Answer: Excessive noise leads to many health problems in humans. Some of them    are:

• Lack of sleep

• Anxiety

• Hypertension, i.e. high blood pressure

• If a person is exposed to excessive noise for an extended period of time, they might temporarily or permanently face hearing loss.