NCERT  ·  Science  ·  Ch.10

Sound

Wave Properties · Speed of Sound · Echo · Resonance · Ultrasound · SONAR

50
Questions
28 min
Duration
3
Tiers
5
Topics
⚡ Begin Analytics
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Question Intelligence

Quiz Analytics

A data-driven breakdown of all 50 questions by difficulty, exam origin and topic distribution.

📈 Distribution Overview

50
Total Questions
CBSE Board
26
State Board
15
Olympiad Level
9

🗂 Topic Coverage

Nature & Propagation of Sound
18%
Characteristics of Sound
18%
Speed of Sound & Echo
24%
Reflection & Resonance
16%
Ultrasound & SONAR
24%
26
CBSE Board
15
State Board
9
Olympiad Level
Conceptual Framework

Key Concept Highlights

6 foundational pillars that power every question in this quiz. Understand these, and the answers follow naturally.

〰️
Nature of Sound
Mechanical, longitudinal wave requiring a medium. Travels as compressions (high pressure) and rarefactions (low pressure). Cannot travel through vacuum. Speed: solid > liquid > gas.
📊
Wave Characteristics
Frequency (f): oscillations per second (Hz). Wavelength (λ): distance between two consecutive compressions. Amplitude (A): maximum displacement. Time period (T) = 1/f.
🔊
Characteristics of Sound
Loudness (amplitude-dependent, dB). Pitch (frequency-dependent — high frequency = high pitch). Timbre/Quality (waveform-dependent, distinguishes instruments at same pitch).
🏔️
Echo & Reverberation
Echo: reflected sound reaching ear after 0.1 s (minimum distance = 17.2 m at 344 m/s). Reverberation: persistence of sound due to repeated reflections. Reduced by soft materials.
🔬
Ultrasound
Frequency > 20,000 Hz. Used in: medical imaging (sonography), detecting defects in metals (non-destructive testing), cleaning, sonar navigation. Bats and dolphins use echolocation.
🌊
SONAR
Sound Navigation And Ranging. Sends ultrasonic pulse, measures time for echo to return. Distance = (speed × time) / 2. Used to map sea floor, detect submarines and fish shoals.
Pedagogical Value

Why MCQs Matter

Multiple-choice questions are not mere guessing games — they are the sharpest diagnostic tool available to a competitive exam aspirant.

~10%

of CBSE Class IX Science — echo numericals and wave properties are board favourites

Quick Reference

Important Formula Capsules

5 must-memorise equations that surface repeatedly across CBSE and JEE papers.

Wave Speed
\[ v = f\lambda = \dfrac{\lambda}{T} \]
Speed of Sound (air)
\[ v \approx 344\ \text{m/s at}\ 22^\circ C \]
Time Period
\[ T = \dfrac{1}{f} \]
Echo Distance
\[ d = \dfrac{v \times t}{2} \]
Min Distance (echo)
\[ d_{\min} = 17.2\ \text{m} \quad (\text{for echo at room temp}) \]
Learning Outcomes

What You Will Learn

By completing this quiz set you will have exercised all the following competencies.

01 Explain how sound is produced and transmitted through a medium as a longitudinal wave
02 Define frequency, wavelength, amplitude, and time period with units
03 Explain the conditions necessary for formation of an echo
04 Solve numerical problems using echo to find distance or speed of sound
05 Distinguish between infrasound, audible range, and ultrasound with examples
06 Describe the working principle of SONAR and solve distance-by-SONAR numericals
Exam Preparation

Strategy & Preparation Tips

4 evidence-based strategies to maximise your score in CBSE Boards and JEE.

01
Step 01
Wave Formula Triangle
v = fλ is the master equation. Given any two of speed, frequency, wavelength — find the third. CBSE numericals always use this in sound context. Practise 10 variations.
02
Step 02
Echo Minimum Distance
Minimum 17.2 m to hear an echo (at room temperature). Derived: 0.1 s × 344 m/s ÷ 2 = 17.2 m. Memorise the derivation, not just the answer — CBSE asks for it.
03
Step 03
SONAR Formula — Halve It
d = v × t/2 (divide by 2 because sound travels TO the object and BACK). Forgetting to halve is the single most common SONAR error. Underline ÷2 in your notes.
04
Step 04
Frequency Ranges List
Infrasound < 20 Hz, Audible 20–20,000 Hz, Ultrasound > 20,000 Hz. Animals: dogs hear 25–65,000 Hz, bats 1,000–100,000 Hz. CBSE directly asks these ranges.

Ready to Test Your Mastery?

50 questions  ·  Elapsed timer  ·  Instant scored results

⚡ Begin Sound Quiz
🎯 Knowledge Check

Science — Sound

50 Questions Class 9 MCQs
1
What is the unit of frequency?
2
Which is necessary for sound to travel?
3
What is the speed of sound in air at room temperature?
4
Which part of the ear vibrates to produce sound sensations?
5
Which property of sound is responsible for 'loudness'?
6
Which part of the ear converts vibrations into electrical signals?
7
Which medium allows sound to travel fastest?
8
What is the range of audible frequency for humans?
9
Which phenomenon is required for echoes?
10
Which application uses ultrasound?
11
What type of wave is sound in air?
12
Which term defines the time taken for one vibration?
13
What is the phenomenon of sound waves bouncing off a surface?
14
What determines the pitch of sound?
15
What happens to sound in vacuum?
16
What is the velocity of sound in water?
17
Which instrument is used to produce a pure note?
18
What produces the sensation of music?
19
What causes noise pollution?
20
Which organ is affected by loud sounds?
21
Which property of sound remains unchanged when it enters new media?
22
Which is NOT a source of noise pollution?
23
Which frequency is ultrasonic?
24
What does SONAR stand for?
25
In a sound wave, regions of high pressure are called:
26
How do plants react to sound?
27
What is ‘reverberation’?
28
Which statement about amplitude is correct?
29
Which sound property helps bats find food at night?
30
What is meant by the ‘period’ of a wave?
31
What type of wave can travel through solids, liquids, and gases?
32
What happens to wavelength if frequency increases?
33
Which component in sound determines ‘quality’ or ‘timbre’?
34
Speed of sound decreases with:
35
Which sound wave travels fastest?
36
What is the SI unit of sound’s loudness?
37
What is the minimum distance for an echo to be heard?
38
What does the term ‘pitch’ mean?
39
What is the principle behind the working of musical instruments?
40
What type of wave is produced by vibrating strings?
41
What is auditory fatigue?
42
What is meant by ‘rare factions’?
43
Sound cannot travel in:
44
What happens when sound travels from air to water?
45
Which component in the ear collects sound waves?
46
What is resonance?
47
What is the scientific term for ‘hearing’?
48
If amplitude doubles, loudness:
49
What is the effect of wind on the speed of sound?
50
What is the role of the auditory nerve?
📚
ACADEMIA AETERNUM तमसो मा ज्योतिर्गमय · Est. 2025
Sharing this chapter
NCERT Class 9 Sound 50 MCQs with Answers
NCERT Class 9 Sound 50 MCQs with Answers — Complete Notes & Solutions · academia-aeternum.com
Prepare thoroughly for NCERT Class IX Science Chapter 11 "Sound" with this expertly designed set of 50 MCQs. These multiple-choice questions cover every important topic, from the basics of sound production, properties of sound waves, pitch and loudness, to applications such as SONAR and ultrasound. Each question is followed by a detailed answer and explanation, making this resource perfect for practice, revision, and exam preparation. Whether you are a student seeking to score high, a teacher…
🎓 Class 9 📐 Science 📖 NCERT ✅ Free Access 🏆 CBSE · JEE
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Exam tip: Sharing chapter notes with your study group creates a reinforcement loop. Teaching a concept is the fastest path to mastering it.

Frequently Asked Questions

An echo is a reflected sound wave that returns to the listener after bouncing off a distant surface.

There must be at least 17 metres between the listener and the reflecting surface. Echoes occur when reflected sound reaches the ear after 0.1 seconds.

By using silencers, planting trees, soundproofing rooms, reducing sources of loud noise, and spreading awareness.

Noise is unpleasant and irregular, while musical sound is pleasant and regular with repeating patterns.

Reverberation is the persistence of sound in a space due to multiple reflections after the original sound has stopped.

A megaphone narrows and directs sound waves, making them travel farther and appear louder.

SONAR (Sound Navigation and Ranging) uses ultrasound to detect objects underwater by measuring reflected sound waves.

Bats emit high-frequency sounds and listen to their echoes to locate prey and avoid obstacles, a process called echolocation.

Excessive sound can cause hearing loss, stress, sleep disturbance, and other health problems.

Ultrasound scans create images of internal organs and monitor pregnancies, without using harmful radiation.

Ultrasound waves can penetrate tissues and reflect off boundaries between different tissues. Computers convert these echoes into images.

Pitch is how high or low a sound is; it depends on the frequency. Higher frequency gives higher pitch.

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    Sound — Learning Resources

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    📚
    ACADEMIA AETERNUM तमसो मा ज्योतिर्गमय · Est. 2025
    Sharing this chapter
    NCERT Class 9 Sound 50 MCQs with Answers
    NCERT Class 9 Sound 50 MCQs with Answers — Complete Notes & Solutions · academia-aeternum.com
    Prepare thoroughly for NCERT Class IX Science Chapter 11 "Sound" with this expertly designed set of 50 MCQs. These multiple-choice questions cover every important topic, from the basics of sound production, properties of sound waves, pitch and loudness, to applications such as SONAR and ultrasound. Each question is followed by a detailed answer and explanation, making this resource perfect for practice, revision, and exam preparation. Whether you are a student seeking to score high, a teacher…
    🎓 Class 9 📐 Science 📖 NCERT ✅ Free Access 🏆 CBSE · JEE
    Share on
    WhatsApp
    Telegram
    X / Twitter
    Facebook
    Instagram
    Threads
    Pinterest
    LinkedIn
    Quora
    Discord
    Reddit
    Email
    academia-aeternum.com/class-9/science/sound/mcqs/ Copy link
    💡
    Exam tip: Sharing chapter notes with your study group creates a reinforcement loop. Teaching a concept is the fastest path to mastering it.

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