Sound Class 9 MCQs with Answers & Explanations
Sound Class 9 MCQs with Answers & Explanations (NCERT-Based)
CBSE Board Examination – Systematic MCQ Practice
Class: 9
Subject: Science
Section: Physics
Topic: Sound
These Multiple Choice Questions (MCQs) are designed strictly as per the NCERT syllabus, making them ideal for CBSE Class 9 Science examinations. Each question includes detailed explanations for better concept clarity.
1. Sound is produced due to:
Answer: B
Sound is produced when objects vibrate. These vibrations disturb surrounding particles and create sound waves.
Sound is produced when objects vibrate. These vibrations disturb surrounding particles and create sound waves.
2. Sound requires a medium for propagation because it is a:
Answer: B
Sound is a mechanical wave and needs a material medium. It cannot travel in vacuum.
Sound is a mechanical wave and needs a material medium. It cannot travel in vacuum.
3. Speed of sound is maximum in:
Answer: C
Particles are closest in solids, so sound travels fastest due to efficient vibration transfer.
Particles are closest in solids, so sound travels fastest due to efficient vibration transfer.
4. Unit of frequency is:
Answer: B
Frequency measures vibrations per second. SI unit is Hertz (Hz).
Frequency measures vibrations per second. SI unit is Hertz (Hz).
5. Audible range for humans is:
Answer: B
Humans hear between 20 Hz and 20 kHz. Below is infrasonic; above is ultrasonic.
Humans hear between 20 Hz and 20 kHz. Below is infrasonic; above is ultrasonic.
6. Time taken for one vibration is:
Answer: C
Time period is the time for one complete oscillation. T = 1/f.
Time period is the time for one complete oscillation. T = 1/f.
7. Pitch depends on:
Answer: B
Higher frequency produces higher pitch (shrill sound).
Higher frequency produces higher pitch (shrill sound).
8. Loudness depends on:
Answer: B
Greater amplitude means louder sound.
Greater amplitude means louder sound.
9. Distance between two compressions is:
Answer: C
Wavelength is distance between successive compressions or rarefactions.
Wavelength is distance between successive compressions or rarefactions.
10. Sound travels as:
Answer: B
Particles vibrate parallel to wave direction, forming compressions and rarefactions.
Particles vibrate parallel to wave direction, forming compressions and rarefactions.
11. Echo is caused by:
Answer: B
Echo occurs when sound reflects from a distant surface and returns.
Echo occurs when sound reflects from a distant surface and returns.
12. Minimum distance for echo:
Answer: C
At least 17 m is needed so reflected sound returns after 0.1 s.
At least 17 m is needed so reflected sound returns after 0.1 s.
13. SONAR works on:
Answer: B
SONAR uses reflection of ultrasonic waves underwater.
SONAR uses reflection of ultrasonic waves underwater.
14. Ultrasound frequency is:
Answer: C
Frequencies above 20,000 Hz are ultrasonic.
Frequencies above 20,000 Hz are ultrasonic.
15. Infrasonic waves are:
Answer: B
Frequencies below 20 Hz are infrasonic.
Frequencies below 20 Hz are infrasonic.
16. Device to measure loudness:
Answer: C
Loudness is measured in decibels using a sound level meter.
Loudness is measured in decibels using a sound level meter.
17. Excess noise causes:
Answer: B
Noise pollution damages hearing ability.
Noise pollution damages hearing ability.
18. Speed of sound in air at room temp:
Answer: A
Approximate speed is 330–343 m/s depending on temperature.
Approximate speed is 330–343 m/s depending on temperature.
19. Wave speed formula:
Answer: A
Speed equals frequency × wavelength.
Speed equals frequency × wavelength.
20. Human voice box is:
Answer: A
Larynx contains vocal cords that vibrate to produce sound.
Larynx contains vocal cords that vibrate to produce sound.