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NCERT solutions for Class 9 Science chapter 12 - Sound

Science Textbook for Class 9

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NCERT Science Class 9

Science Textbook for Class 9 -

Chapter 12: Sound

Chapter 12: Sound solutions [Page 162]

Q 1 | Page 162

How does the sound produced by a vibrating object in a medium reach your ear?

Chapter 12: Sound solutions [Page 163]

Q 1 | Page 163

Explain how sound is produced by your school bell.

Q 2 | Page 163

Why are sound waves called mechanical waves?

Q 3 | Page 163

Suppose you and your friend are on the moon. Will you be able to hear any sound produced by your friend?

Chapter 12: Sound solutions [Page 166]

Q 1.1 | Page 166

Which wave property determines loudness?

Q 1.2 | Page 166

Which wave property determines pitch?

Q 2 | Page 166

Guess which sound has a higher pitch: guitar or car horn?

Chapter 12: Sound solutions [Page 166]

Q 1 | Page 166

What are wavelength, frequency, time period and amplitude of a sound wave?

Q 2 | Page 166

How are the wavelength and frequency of a sound wave related to its speed?

Q 3 | Page 166

Calculate the wavelength of a sound wave whose frequency is 220 Hz and speed is 440 m/s in a given medium.

Q 4 | Page 166

A person is listening to a tone of 500 Hz sitting at a distance of 450 m from the source of the sound. What is the time interval between successive compressions from the source?

Chapter 12: Sound solutions [Page 166]

Q 1 | Page 166

Distinguish between loudness and intensity of sound.

Chapter 12: Sound solutions [Page 167]

Q 1 | Page 167

In which of the three media, air, water or iron, does sound travel the fastest at a particular temperature?

Chapter 12: Sound solutions [Page 168]

Q 1 | Page 168

An echo returned in 3 s. What is the distance of the reflecting surface from the source, given that the speed of sound is 342 m s−1?

Chapter 12: Sound solutions [Page 169]

Q 1 | Page 169

Why are the ceilings of concert halls curved?

Chapter 12: Sound solutions [Page 170]

Q 1 | Page 170

What is the audible range of the average human ear?

Q 2.1 | Page 170

What is the range of frequencies associated with Infrasound?

Q 2.2 | Page 170

What is the range of frequencies associated with Ultrasound?

Chapter 12: Sound solutions [Page 172]

Q 1 | Page 172

A submarine emits a sonar pulse, which returns from an underwater cliff in 1.02 s. If the speed of sound in salt water is 1531 m/s, how far away is the cliff?

Chapter 12: Sound solutions [Pages 174 - 175]

Q 1 | Page 174

What is sound and how is it produced?

Q 2 | Page 174

Describe with the help of a diagram, how compressions and rarefactions are produced in air near a source of sound.

Q 3 | Page 174

Cite an experiment to show that sound needs a material medium for its propagation.

Q 4 | Page 174

Why is sound wave called a longitudinal wave?

Q 5 | Page 174

Which characteristics of the sound helps you to identify your friend by his voice while sitting with others in a dark room?

Q 6 | Page 174

Flash and thunder are produced simultaneously. But thunder is heard a few seconds after the flash is seen, why?

Q 7 | Page 174

A person has a hearing range from 20 Hz to 20 kHz. What are the typical wavelengths of sound waves in air corresponding to these two frequencies? Take the speed of sound in air as 344 m s−1.

Q 8 | Page 174

Two children are at opposite ends of an aluminium rod. One strikes the end of the rod with a stone. Find the ratio of times taken by the sound wave in air and in aluminium to reach the second child.

Q 9 | Page 174

The frequency of a source of sound is 100 Hz. How many times does it vibrate in a minute?

Q 10 | Page 174

Does sound follow the same laws of reflection as light does? Explain.

Q 11 | Page 174

When a sound is reflected from a distant object, an echo is produced. Let the distance between the reflecting surface and the source of sound production remains the same. Do you hear echo sound on a hotter day?

Q 12 | Page 174

Give two practical applications of reflection of sound waves.

Q 13 | Page 174

A stone is dropped from the top of a tower 500 m high into a pond of water at the base of the tower. When is the splash heard at the top? Given, g = 10 m s−2 and speed of sound = 340 m s−1.

Q 14 | Page 174

A sound wave travels at a speed of 339 m s−1. If its wavelength is 1.5 cm, what is the frequency of the wave? Will it be audible?

Q 15 | Page 175

What is reverberation? How can it be reduced?

Q 16 | Page 175

What is loudness of sound? What factors does it depend on?

Q 17 | Page 175

Explain how bats use ultrasound to catch a prey.

Q 18 | Page 175

How is ultrasound used for cleaning?

Q 19 | Page 175

Explain the working and application of a sonar.

Q 20 | Page 175

A sonar device on a submarine sends out a signal and receives an echo 5 s later. Calculate the speed of sound in water if the distance of the object from the submarine is 3625 m.

Q 21 | Page 175

Explain how defects in a metal block can be detected using ultrasound.

Q 22 | Page 175

Explain how the human ear works.

Chapter 12: Sound

NCERT Science Class 9

Science Textbook for Class 9 -

NCERT solutions for Class 9 Science chapter 12 - Sound

NCERT solutions for Class 9 Science chapter 12 (Sound) include all questions with solution and detail explanation. This will clear students doubts about any question and improve application skills while preparing for board exams. The detailed, step-by-step solutions will help you understand the concepts better and clear your confusions, if any. has the CBSE Science Textbook for Class 9 solutions in a manner that help students grasp basic concepts better and faster.

Further, we at are providing such solutions so that students can prepare for written exams. NCERT textbook solutions can be a core help for self-study and acts as a perfect self-help guidance for students.

Concepts covered in Class 9 Science chapter 12 Sound are Structure of the Human Ear (Auditory Aspect Only), Applications of Ultrasound - SONAR, Range of Hearing in Humans, Uses of Multiple Reflection of Sound, Reflection of Sound - Reverberation, Reflection of Sound - Echo, Speed of Sound in Different Media, Sound Waves Are Longitudinal Waves, Sound Needs a Medium to Travel, Propagation of Sound, Production of Sound, Sound (Numerical).

Using NCERT Class 9 solutions Sound exercise by students are an easy way to prepare for the exams, as they involve solutions arranged chapter-wise also page wise. The questions involved in NCERT Solutions are important questions that can be asked in the final exam. Maximum students of CBSE Class 9 prefer NCERT Textbook Solutions to score more in exam.

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