Important Questions Class 8 Science Chapter 13

Important Questions Class 8 Science Chapter 13 – Sound. 

Science plays a vital role in building a student’s career as it is included as a core subject in almost every field. To be good in Science, students need to practise consistently. 

Chapter 13 of Class 8 Science is about ‘Sound’. The important topics covered in Chapter 13 include:

• • How sound is produced?
  • Different types of sound made by humans
  • Medium for sound propagation
  • Human ear and mechanism of sound production by ear
  • Amplitude and time period. Frequency of a vibration
  • Noise pollution and its prevention
  • Audible and inaudible sounds 

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For students to score well, it is very important that none of the topics covered in any chapter remain untouched. Extramarks has included all the major questions to boost students’ performance in their examinations in our question bank Important Questions Class 8 Science Chapter 13.  By practising questions from our Important Questions Class 8 Science Chapter 13 students will recall all the concepts covered in the chapter Sound. One can find problems in the NCERT textbook, the NCERT exemplar, and other reference sources. A team of experts selects the questions. After a thorough understanding of the questions, experienced science teachers provide comprehensive solutions, ensuring that students are studying from the correct material.

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Important Questions Class 8 Science Chapter 13 – With Solutions

We have provided a comprehensive collection of questions along with their detailed solutions in the Important Question Class 8 Science Chapter 13. The questions cover all topics in the chapter. After referring to andsolving these questions, students can recall all the interrelated concepts of Sound efficiently.

Below are a few sample questions and answers from our question bank of Class 8 Science Chapter 13 Important Questions.

Question 1. Define frequency. 

Answer 1. Frequency is the number of total oscillations per second. 

Question 2. What is the unit of frequency? 

Answer 2. ‘Hertz’ is a unit of measurement for frequency. The symbol for it is Hz.

Question 3. _______ and _______ are two important properties of any sound. 

Answer 3. Frequency and amplitude are the two important properties of any sound.

Question 4. In humans, sound is produced by the ______________. 

Answer 4. The voice box, or larynx produces Sound in humans. 

Question 5. The range of audible frequencies for the human ear is roughly from ______ to ______ Hz. 

Answer 5.  The range of audible frequencies for the human ear is roughly from __20____ to __20,000____ Hz. 

Question 6. Define noise. 

Answer 6. Noise is the name given to all unpleasant sounds.

Question 7. Give two examples of noise pollution.

Answer 7. During an event, the use of firecrackers and loudspeakers.

Question 8. Explain, with an example, that sound travels in liquids. 

Answer 8. Fill a bucket with water and,  using your one hand, try to shake a bell under the water. And make sure that the bell does not touch the bucket inside. Now carefully place your ear on the water’s surface. When you put your ear, you will hear the sound of a ringing bell. This proves that sound can travel through water.

Question 9. Give an example to show that frequency determines the shrillness or pitch of a sound. 

Answer 9. A drum produces a low-frequency vibration. And it makes a low-pitched sound. Conversely, a whistle has a high frequency and generates a higher pitch sound.

Question 10. Demonstrate an activity to show that sound requires a proper medium for propagation 

Answer 10. 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 sharp attention to the ring. Now, wrap your hands around the tumbler’s rim. Place your mouth in the space made by your hands. Tell your friend to ring the phone again.. While sucking air from the tumbler, try to listen to the ring. Keep one eye on the tumbler and take it out of your mouth. The decreased air volume in the tumbler probably contributed to the ring’s reduced volume. There will be no sound if the tumbler is entirely devoid of air. This demonstrates that sound requires a medium to travel.

Question 11. Write the difference between noise and music. Can music become noise sometimes?

Answer 11. Music is a sound which we feel is pleasant to hear. Sounds from pianos, flutes, and violins are melodic to hear.

Noise is defined as unpleasant sounds to hear.

The sounds which are unpleasant to hear are-

(a) Sounds from bus and truck horns.

(b) Electrical generator sound.

(c) Gunshot Sound.

(d) Jackhammer sound.

Yes, sometimes, when we play music at high volumes, it is also called noise.

Question 12. Your parents are going to purchase a house. They have been offered one house on the roadside. While the other is three lanes away from the roadside. Which place would you suggest your parents  buy it? Explain your answer.

Answer 12. It is better to buy a house which is located three lanes away from the main road. In this house, there would be less noise compared to the house on the main road. The noise can be caused by various commuting vehicles and people on the main road. As the distance between the original noise source and the listener increases, the sound and intensity of the noise decrease. So it is better to buy the house that is three lanes away.

Question 13. We know that vibration is necessary for producing sound, so why can’t we hear the sound produced by every vibrating body?

Answer 13. Everyone has their own set of frequencies.But as humans, we can only hear frequencies that range between 20 Hz and 2000 Hz. So humans cannot hear any sound from a lot of other vibrating bodies.

Question 14. Assume that a stick is stuck against a frying pan in a vacuum.Explain whether or not the frying pan will vibrate.Will humans be able to hear the sound? 

Answer 14. The frying pan will vibrate, but human ears will not be able to hear the vibrating sound of the frying pan as sound cannot travel within a vacuum.

Question 15. Two astronauts are floating near each other in space. Can they both talk to each other without using any unique devices? Give reasons.

Answer 15. There will be no  medium for sound waves to travel in space, and it will be a vacuum. Sound cannot travel in a vacuum; hence, sound cannot be heard without any unique device.

Question 16. The town hall building is situated near Boojho house. A clock is on the top of the town hall building. The clock rings the bell every hour. Boojho has observed that the sound of the clock ring appears to be clearer at night. Explain.

Answer 16. When sound is initiated, speed, pitch, and loudness are all initiated with vibration. During the daytime, there are several vibrations around us. This results in a decrease in the amplitude of vibrations. At night, there will be no such distractions, which will make the sound clearer.

Question 17. How is the sound produced, and how does it get transmitted and heard by us?

Answer 17. 

Sound is generally produced when the body starts to vibrate by any given force. This vibration produces multiple waves, which travel through a medium to reach their destination (our ears), where they are heard.

Humans hear the sound with our ears. The shape of the outer part of our ear is funnel-like. When the sound enters our ears, it travels all the way down to a canal at the end, where there is a delicately stretched membrane. The membrane is called the eardrum. Our eardrum is like a stretched rubber sheet. The sound vibrations will make the eardrum vibrate. The eardrum sends vibrations to the inner side of the ear. The signal from these vibrations goes to the brain.That is how we hear the sound.

Question 18. Name the characteristic of Sound that enables us to distinguish between a man’s and woman’s voices even without seeing them.

Answer 18. The pitch of the Sound allows us to distinguish between a man’s and woman’s voices even without seeing them.

Question 19. Lightning and thunder happen in the sky simultaneously and at the same distance from us. Then why do we first see the flash of lightning and then, after some time we hear the thunder sound?

Answer 19. Lightning and thunder occur  in the sky simultaneously and at the same distance from us. But we first see the flash of lightning, and then, after some time, we hear the thunder sound. This is because the velocity of light in air is 3× 108 m/s while the velocity of Sound in  air is 343 m/s.

Question 20. Explain with an activity how  a vibrating object produces sound.

Answer 20. Take a metal dish, pour water into it, and strike its edge with a spoon. You will hear a sound. Again, strike the edge of the dish and look at the surface of the water inside it. You will observe that the vibrating dish produces a sound along with waves in the water. This shows that there is vibration in the dish, which is producing sound.

Question 21. How is sound produced from a guitar?

Answer 21. The sitar string is plucked to produce sound, along with the string’s other parts.The instrument is forced to vibrate, and we hear the Sound of the instrument’s vibration.

Question 22. What is an eardrum?

Answer 22. The eardrum, or tympanum, is a thin, funnel-shaped membrane that separates the external ear from the middle ear in humans; it is like a stretched rubber sheet, and sound vibrations make the eardrum vibrate. The eardrum sends a vibration to the inner ear, and from there, the signal is sent to the brain; in this way, we can hear the sounds around us.

 Question 23. Explain noise pollution and its causes.

Answer 23. The presence of excessive or undesirable sounds in the environment is called noise pollution. The main causes of noise pollution are the sounds made by the horns of vehicles, the sounds coming from construction sites, the sounds produced by factory machinery, etc. In our homes, the sounds produced by television, transistor radios at high volumes, air conditioners, coolers, and some kitchen appliances like pressure cookers contribute to noise pollution.</spa

 Question 24. Name the organ in humans that produces Sound. How does it work?

Answer 24. In humans, sound is produced by the voice box or larynx.The larynx has two vocal cords stretched across it, so it leaves a slit for air passage. When our lungs force air through the slit, both the vocal cords vibrate to produce Sound.

Question 25. Explain that  Sound needs a medium for propagation.

Answer 25. Take a metal glass tumbler. Place a cell phone in it. Ask your friend to give you a ring on this cell phone. Listen to the ring with care. Now surround the rim of the tumbler with your hands. Put your mouth on the opening in between your hands. Tell your friend  to give him a ring again. Listen to the ring while inhaling air from the tumbler. The Sound becomes significantly less. This shows that the sound needs a medium to propagate.

Question 26. What are the two essential properties of Sound?

Answer 26. (i) Amplitude- It is the maximum displacement from the original position of an oscillatory body. It controls the loudness of a sound. The greater the amplitude, the louder the Sound is.

(ii) Frequency – The number of oscillations happening in one second is called the frequency. The frequency controls the pitch of the sounds. High-pitched Sound means high frequency. The unit of frequency is hertz.

  Question 28. Why are some sounds louder than others?
Answer 28. The loudness of Sound depends upon its amplitude—the larger the amplitude of vibration, the louder the Sound and vice versa.

 Question 29. Discuss the importance of Sound in our lives.

Answer 29. Sound plays an essential role in our lives; Sound helps us  communicate with one another. Sound is so important because animals can hear events around them, regardless of where their attention is focused.

Question 30. Describe the oscillatory motion.

Answer 30. Oscillation is the process of sliding to and fro uninterruptedly, and oscillation motion is the movement created by this process.

Question 31. What are the harmful effects of noise pollution?

Answer 31. Excessive noise leads to many severe health problems in humans. Some of them are as follows-

• • 1. i) Lack of sleep
    2. ii) Anxiety

iii)Hypertension, i.e. high blood pressure

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

Question 32. What is the relation between an oscillating body’s ‘time-period’ and ‘frequency’?

Answer 32. time period is the reciprocal of the frequency.

Time period = 1/frequency.

Question 33. Why can we not hear the screams of a bat?

Answer 33. The frequency of bat screams is 20,000 Hz. That’s why we cannot hear the scream of a bat.

Question 34. State the following statements are true or false-

(a) Sound cannot travel in vacuum.

(b)Number of oscillations per second of a vibrating object is known as its time period.

(c) If the amplitude of the vibrations is large, then the Sound is feeble.

(d) lower is the frequency of vibration, the higher the pitch.

(e) If the amplitude of the vibrations is doubled, the loudness of the Sound will also be doubled.

(f) If the amplitude of vibrations is halved, the loudness of Sound becomes one-fourth time.

(g) Any unwanted or unpleasant Sound is termed as music.

(h) Noise pollution can cause partial hearing impairment.

Answer 34. (a) True

(b) False

(c) False

(d) False

(e) True

(f) False

(g) False

(h) True

Question 35. Explain why the voices of men, women, and children are different.

Answer 35. The reason for the difference in voices is the length of the vocal cords. The longest vocal cord is in men, and the shortest vocal cord is in women. Children have the smallest vocal chord.

Benefits of Solving Important Questions Class 8 Science Chapter 13-

Science is a subject that requires a lot of reading and multiple revisions. Students are advised to register on the Extramarks website and gain access to Important Questions Class 8 Science Chapter 13. Students will get a sense of confidence by solving all questions and by referring to the detailed step-by-step solutions given for each question. These answers are prepared by Science teachers with decades of teaching experience, so students can confidently rely on the quality and authenticity of all our solutions.

Following are a few additional benefits of practising from our Chapter 13 Class 8 Science Important Questions:

• • 1. 1. • In our Important Questions Class 8 Science Chapter 13, we have included different sets of questions from various references and sources that will aid students in understanding every concept included in the chapter in the form of questions and getting command over the subject.
          • There is a high chance that the questions included in our question bank will come in the school exams. So students will benefit from practising questions that are similar to exam questions. This will boost students’ confidence and help them score well in exams.All our solutions are prepared as per the CBSE syllabus and latest NCERT guidelines. So students can be 100% sure about the relevance of these answers.

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