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All questions of Propagation Of Sound Waves for Class 9 Exam

What is the audible range of human hearing?
  • a)
    20 kHz to 40 kHz
  • b)
    20 Hz to 20 kHz
  • c)
    0 Hz to 20 Hz
  • d)
    10 Hz to 10 kHz
Correct answer is option 'B'. Can you explain this answer?

Arizona Academy answered
Humans can typically hear sounds in the frequency range of 20 Hz to 20 kHz. This range can vary based on age and individual sensitivity, with younger people often able to hear higher frequencies.
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How does wind direction affect the speed of sound?
  • a)
    Increases speed against the wind
  • b)
    Decreases speed in still air
  • c)
    It has no effect
  • d)
    Increases speed with the wind
Correct answer is option 'D'. Can you explain this answer?

Arizona Academy answered
The speed of sound increases when the wind blows in the same direction as the sound. Conversely, it decreases if the wind is blowing against the sound's direction.

What is the term for sound frequencies above 20 kHz?
  • a)
    Sonic sound
  • b)
    Audible sound
  • c)
    Ultrasonic sound
  • d)
    Infrasonic sound
Correct answer is option 'C'. Can you explain this answer?

Arizona Academy answered
Ultrasonic sound refers to frequencies above 20 kHz, which are inaudible to humans but can be detected by some animals and are used in various technological applications.

What phenomenon explains why you see lightning before you hear thunder?
  • a)
    Sound reflects off the ground
  • b)
    Both travel at the same speed
  • c)
    Light travels faster than sound
  • d)
    Sound travels faster than light
Correct answer is option 'C'. Can you explain this answer?

Arizona Academy answered
Light travels much faster than sound. The speed of light in air is approximately 3 × 10^8 m/s, while sound travels at about 343 m/s in air, which is why we see lightning first before hearing the thunder.

Which of the following correctly describes the relationship between frequency and wavelength?
  • a)
    They are inversely proportional
  • b)
    They have no relationship
  • c)
    They are directly proportional
  • d)
    They are equal
Correct answer is option 'A'. Can you explain this answer?

Arizona Academy answered
Frequency and wavelength are inversely proportional; as the frequency of a wave increases, its wavelength decreases. This relationship is expressed mathematically as wave velocity being the product of frequency and wavelength.

What is the typical speed of sound in water at 0°C?
  • a)
    5100 m/s
  • b)
    330 m/s
  • c)
    6000 m/s
  • d)
    1450 m/s
Correct answer is option 'D'. Can you explain this answer?

Arizona Academy answered
The speed of sound in water at 0°C is approximately 1450 m/s, which is significantly faster than in air due to the higher density and elasticity of water compared to gases.

What is the primary source of sound?
  • a)
    Vibrating objects
  • b)
    Thermal energy
  • c)
    Electrical signals
  • d)
    Light
Correct answer is option 'A'. Can you explain this answer?

Arizona Academy answered
Sound is primarily produced by vibrating objects, which create mechanical waves that travel through a medium. When these vibrations disturb the surrounding particles, they generate sound waves that we can hear.

What happens to sound intensity as it travels through a vacuum?
  • a)
    It becomes inaudible
  • b)
    It cannot travel
  • c)
    It increases
  • d)
    It decreases
Correct answer is option 'B'. Can you explain this answer?

Arizona Academy answered
Sound cannot travel through a vacuum because there are no particles to transmit the mechanical vibrations necessary for sound propagation. Thus, sound intensity cannot be measured in a vacuum.

What type of wave is primarily associated with sound?
  • a)
    Transverse wave
  • b)
    Surface wave
  • c)
    Longitudinal wave
  • d)
    Electromagnetic wave
Correct answer is option 'C'. Can you explain this answer?

Arizona Academy answered
Sound travels mainly as longitudinal waves, where the particles of the medium vibrate in the same direction as the wave travels, creating areas of compression and rarefaction.

Chapter doubts & questions for Propagation Of Sound Waves - Physics Class 9 ICSE 2025 is part of Class 9 exam preparation. The chapters have been prepared according to the Class 9 exam syllabus. The Chapter doubts & questions, notes, tests & MCQs are made for Class 9 2025 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests here.

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