Class 9 • Physics • Chapter 10
Sound
True & False Quiz
Vibrate. Propagate. Echo.
✓True
✗False
25
Questions
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Ch.10
Chapter
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IX
Class
Why True & False for Sound?
How this format sharpens your conceptual clarity
🔵 Sound connects physics to everyday life — from sonar and medical ultrasound to music and the limits of human hearing.
✅ T/F tests longitudinal vs transverse waves, frequency ranges (infrasonic/audible/ultrasonic), echo conditions, and applications of ultrasound/SONAR.
🎯 Sound is a LONGITUDINAL mechanical wave — it requires a medium to travel (it cannot travel through vacuum, unlike light).
📋
Read each statement carefully. Click True or False — instant feedback with explanation appears. Submit anytime; unattempted questions are marked Skipped.
Q 1
Sound can travel through a vacuum.
Q 2
The unit of frequency is Hertz (Hz).
Q 3
Sound waves in air are longitudinal waves.
Q 4
Humans can hear sounds of frequency 5 Hz.
Q 5
The amplitude of a sound wave determines its pitch.
Q 6
The cochlea in the ear helps convert sound vibrations to nerve signals.
Q 7
Sound travels faster in air than in water.
Q 8
Bats use ultrasound to locate prey.
Q 9
Loud sounds can damage our hearing.
Q 10
Velocity of sound is constant in all mediums.
Q 11
Sound reflected from a distant barrier is called an echo.
Q 12
SONAR is used to detect objects under water.
Q 13
All musical sounds are a result of regular vibrations.
Q 14
Noise is produced by irregular vibrations.
Q 15
Sound does not need a medium for propagation.
Q 16
Reverberation is the persistence of sound due to multiple reflections.
Q 17
Pitch of sound depends on its amplitude.
Q 18
The part of the ear that vibrates when sound reaches it is called the eardrum.
Q 19
Higher amplitude means lower loudness.
Q 20
Rarefactions are regions of high pressure in a sound wave.
Q 21
Ultrasound waves are above 20,000 Hz frequency.
Q 22
Sound travels faster in solids than in liquids.
Q 23
Birds use sound for communication.
Q 24
Frequency of a sound wave changes when it enters a new medium.
Q 25
Musical instruments produce sound by vibrating air, strings, or membranes.
Key Takeaways — Sound
Core facts for CBSE Boards & exams
1
Sound is a longitudinal mechanical wave — particles vibrate parallel to direction of propagation.
2
Speed of sound in air at 25°C ≈ 346 m/s; faster in liquids and solids than in gases.
3
Frequency: Infrasonic < 20 Hz; Audible 20–20,000 Hz; Ultrasonic > 20,000 Hz.
4
Echo: reflected sound heard after original; minimum distance for echo = 17.2 m (in air).
5
Reverberation: persistence of sound due to multiple reflections in an enclosed space.
6
SONAR: Sound Navigation And Ranging — uses ultrasound to measure ocean depth and detect objects underwater.