NCERT Solutions Class 9 Science Chapter 12

NCERT Solutions for Class 9 Science Chapter 12: Sounds

Science is a fascinating subject that demands a higher understanding level and it opens a lot of opportunities for the students who wish to make a career in the field of Engineering and Sciences. Class 9 is a  crucial  stage for the students as it prepares them for the higher  classes and entrance exams.. Therefore, students need to grasp each concept with examples and exercises for an in-depth understanding. 

Class 9 Science Chapter 12: Sounds quenches the students curiosity on sound-related questions. The chapter deals with concepts like sound production with the help of an activity using a tuning fork.   The illustration with the help of the bell jar experiment justifies  the fact that sound needs a medium to travel. In addition, students will learn the properties and characteristics of sound waves, which are also discussed comprehensively. Further, they  will learn the difference between longitudinal waves and transverse waves. 

NCERT Solutions for Class 9 Chapter 12 are available on  Extramarks’ website for  students. It is the best way to enhance one’s conceptual knowledge of the topic. It contains answers to the questions provided in the NCERT textbook so that students can understand easily and  quickly.  . Our NCERT solutions are a reference guide to clarify topic-related doubts. The solutions contain several long, short answers along with MCQs and important questions answered by the subject matter experts. 

Extramarks is  one of the leading online platforms and is most trusted by the lakhs of students. The chapter sound is important  from the examination point of view.. Students can go through our NCERT solutions Class 9 Science Chapter 12 for self-evaluation after studying each chapter. With this help, students will get to know their shortcomings, and need a little more practise  to overcome them before the examination. 

Students can visit our website for the latest information and exam-related news on the NCERT syllabus. Further, students can also refer to  NCERT Solutions Class 10, NCERT Solutions Class 11, and NCERT Solutions Class 12.

Key Topics Covered In NCERT Solutions for Class 9 Science Chapter 12:

NCERT solutions for Class 9 Science Chapter 12 explains new terms and definitions related to sound. Here, students will learn about sound production with the help of activity using a tuning fork.  They will also learn about the characteristics of a sound like pitch, loudness, softness, tone, and noise. It also discusses the values of the speed of sound in different media and reverberations. 

Some of the key topics featured in NCERT Solutions for Class 9 Science Chapter 12 are: 

1. Production of Sound

A ringing bell or thunderclap is one noise, while laughter or rock music is another. All sounds are waves, and therefore, all sounds are the same. Let’s examine how we can apply wave qualities to sound.

A sound is a form of energy transmitted as waves to our ears and for example, when we speak, our vocal cords vibrate. The  string of a guitar vibrates back and forth to produce sound. A tuning fork vibrates and makes a sound. A rattle produces a sound when shaken. Sound waves cannot travel in a vacuum, so they must travel through a medium.

Because sound waves vibrate your ears, you can hear them when they reach your ears. Your brain then relays the vibrations to you via nerves. The brain then converts the messages into sound. Students can refer to NCERT Solutions for Class 9 Science Chapter 12 to understand the production of sound and its fundamentals concepts. 

2. Propagation of Sound

A longitudinal wave is a wave motion where the particles of the medium oscillate around their mean positions in the wave propagation direction.

The most common sound wave type is the longitudinal one.

Let’s take a look at the way sound waves travel. Use a tuning fork to shake. Now, focus on prong A. Figure (a) shows the tuning fork’s normal position and the initial state of air particles. As prong A moves to the right, compressed air particles are generated, as shown in figure (b). Vibrating air layers cause the compression to continue forward.

As prong A returns to its original position, the pressure on its right decreases, creating a rarefaction. This rarefaction is a disturbance that travels forward like compression. As a result, calculating sound propagation can be difficult. Thus, students can solve examples in NCERT Solutions for Class 9 Science Chapter 12. 

3. Reflection of Sound

Sound waves bounce back when they collide with solid or liquid surfaces. Sound waves are subject to the same rules as light waves. Sound waves must reflect on a large surface or obstruction to do so. For example, the rolling of thunder is caused by successive reflections from terrain and clouds. As per the rule of sound reflection, the directions in which sound is incident and reflected would make equal angles with the normal to the reflecting surface. And all the three would lie in the same plane.

There are three applications of the principle of reflection elaborated in NCERT Solutions for Class 9 Science Chapter 12 are:

  • Megaphone: A megaphone refers to a tube that looks like a horn. Consecutive reflections keep sound waves from spreading outside the box, limiting them to the air inside.
  • Hearing Aid : A hearing aid is a device that helps people  who are hard of hearing. The hearing aid’s sound waves are reflected in a smaller area that leads to the ear.
  • Soundboards: Curved surfaces can reflect sound waves. This reflection of sound waves can be used to distribute them around an auditorium evenly. Soundboards are used to reflect sound waves at the source. The speaker’s position is the excellent board’s focal point.

4. Range of hearing 

Vibrating sources emit sound waves that are then carried through the air. The human ear can hear sound waves between 20 Hz to 20 kHz. This is known as the audible range. Ultrasonic waves, also known as ultrasound, are sound waves with frequencies higher than the audible range. Infrasonic sounds are sound waves that have frequencies below the hearing range.

Applications of ultrasound elaborated in NCERT Solutions for Class 9 Chapter 12 

  • It is used for medical diagnosis and treatment as well as surgical procedures.
  • Bats and porpoises use ultrasound to navigate in the dark and find food.
  • It is used to detect a defective foetus.
  • It is used to treat muscular pain.
  • Ultrasonography is a technique that uses ultrasonic waves and creates 3-dimensional images to locate eye tumours.
  • Ultrasound waves are also commonly used to clean spiral tubes and electronic components.
  • To find cracks and flaws in metal blocks, ultrasound is used to inspect them.

5. Sonar

One of the essential uses of sound reflection is oceanographic research. This is done using SONAR. In addition, SONAR technology can detect submerged ships, sunken ships, and icebergs not visible from the surface. Sonar sends ultrasonic waves to the boat in all directions, which are then reflected. To understand the concept of SONAR, students can refer to NCERT Solutions for Class 9 Chapter 12. 

6. Structure of the human ear 

Structure of the Human Ear – The human ear has a sensitive apparatus that allows us to hear. The three main ear sections are the outer, middle, and inner. Further, each component of an ear is responsible in its way for decoding and interpreting sound. For example, Pinna refers to the outer ear. It transports sound from the middle ear to the auditory canal.

The eardrum (also known as the Tympanic Membrane) is a thin membrane located at the terminus of the auditory channel. The eardrum pushes inwardly and outwardly as the rarefaction or compression reaches it. This causes the eardrum to vibrate. These vibrations of the eardrum are amplified by the three bones of the middle ear: the hammer(malleus), the anvil (incus), , and the stirrup(stapes).

The middle ear transmits these vibrations to the inner ear. The inner ear converts pressure fluctuations and vibrations into electrical signals. In addition, the auditory nerve sends these electrical signals to the brain. The brain interprets them as sound.

Students can refer to NCERT Solutions for Class 9 Chapter 12 to further study the functions and structure  of the human ear. 

NCERT Solutions for Class 9 Science Chapter 12: Exercise &  Solutions

NCERT Solutions for Class 9 Chapter 12 Students can go through  Extramarks NCERT solutions to get answers to the questions that they need to practise before exams.  The solutions are prepared by experienced subject matter experts  per the latest CBSE guidelines. It helps students to improve their grades considering that Science is a scoring subject.. Our solutions guide can help students revise the complete syllabus by understanding the key topics and  get excellent results in the examination.. 

Chapter 12 Class 9 Science deals with concepts like sound production, characteristics of sound waves, and concepts of frequency. Students will learn about the difference between longitudinal and transverse waves. In addition, they  will learn about the formula for the period of the sound wave length with its SI unit. It also discusses the characteristics of a sound like pitch, loudness, and softness. 

Students can refer below for specific exercise, examples  and solutions:

  • Class 9 Science Chapter 12: Exercise 12.1 – Examples and Solutions
  • Class 9 Science Chapter 12: Exercise 12.2 – Examples and Solutions
  • Class 9 Science Chapter 12: Exercise 12.3 – Examples and Solutions
  • Class 9 Science Chapter 12: Exercise 12.4 – Examples and Solutions
  • Class 9 Science Chapter 12: Exercise 12.5 – Examples and Solutions

 besides  this, students may  also refer to  solutions for primary and secondary Classes from 1 to 12:

  • NCERT Solutions Class 1
  • NCERT Solutions Class 2
  • NCERT Solutions Class 3
  • NCERT Solutions Class 4
  • NCERT Solutions Class 5
  • NCERT Solutions Class 6
  • NCERT Solutions Class 7
  • NCERT Solutions Class 8
  • NCERT Solutions Class 9
  • NCERT Solutions Class 10
  • NCERT Solutions Class 11
  • NCERT Solutions Class 12

NCERT Exemplar for Class 9 Science:

Science is a subject that requires a much deeper understanding to comprehend the concepts. Therefore, solving  questions with varying degrees of difficulty  level  will help students remember the definitions, formulas, concepts  more precisely. In addition, they can evaluate their preparation strategies to master the subject. 

The NCERT exemplar is designed especially for competitive exams; it comprises  MCQs, new concepts, and skill-developing questions. It will help students generalise the concepts and expose them to multiple concept-based questions. The Exemplar prepares  students  for problems of higher aptitude level and focuses more on applying concepts learned in class. Students can refer to NCERT exemplar textbooks and start their preparation. NCERT books won’t be enough to get an outstanding result, you need to supplement your preparation with NCERT solutions followed by exemplar to maximise your potential and ace the exam with flying colours. 

Some of the questions from NCERT Solutions for Class 9 Chapter 12 are taken and provided in the  exemplar. It has detailed explanations and answers. The Exemplar covers basics on all topics for students besides advanced level information.  

Key Features of NCERT Solutions for Class 9 Science Chapter 12:

Class 9 Science NCERT Solutions Chapter 12 includes all essential topics mentioned earlier in this article such as the production of sound, characteristics of sound waves, and longitudinal waves. In addition, the students will learn more about the sound wave’s frequency, amplitude, and speed. Sound also includes concepts like the reflection of sound, echo, reverberations, and uses of multiple reviews of sounds, ultrasound, and sonar. 

These are the key concepts from NCERT Solutions for Class 9 Science Chapter 12: 

  • Students can refer to solutions and learn the main topics and sub topics  with an in-depth understanding and conceptual clarity.  
  •  To solve the problems using different methods are provided.
  • The problems are solved using their expertise,  skills, and thematic understanding of the chapter.
  • Solutions can be used as a reference for further study, review, and practice examples and in text and end text exercises to assess their understanding  of the chapter.They can cross check their answers from solutions and gauge their preparation level.

FAQs (Frequently Asked Questions)

The chapter sound includes essential sub- topics such as reflection of sound, echo, reverberations, uses of multiple sound reviews, ultrasound, and sonar. The main topics are listed below: :

  • Production of Sound
  • Propagation of Sound
  • Reflection of Sound
  • Range of Hearing
  • Applications of Ultrasound
  • Sonar
  • Structure of Human Ear

The vibration of objects produces sound, which is a form of energy. Vibration is the rapid to-and-fro movement of an object. According to the theory, vibration is caused by particles causing a disturbance in the medium. For example, a rubber band can vibrate and produce sound by being stretched. The vibrating body can travel through the medium, but the particles cannot move forward. This is how sound is created.

SONAR stands for sound, navigation, and range. SONAR is an acoustic device that measures underwater objects’ speed, direction, and depth. Submarines, for example, use SONAR to communicate or detect   different objects like submarines, sunken ships etc.  underwater. It produces an ultrasonic sound and is designed to travel below the seawater. The transducer transmits this sound. The detector records the echo produced when an object reflects it. The sensor converts the detected signal into electrical signals that can be used for measurement.