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CBSE Class 9 Sound — practice questions — page 2

Explore 50 free Sound questions in CBSE Class 9 Science. Open each question or exercise to read its content, reference answers and available explanation.

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Sound questions and exercises with answers

Showing questions 31–50 of 50.

Speed of sound in air is roughly:Read the answer and worked solution →How is sound INTENSITY related to the SQUARE of the AMPLITUDE?Read the answer and worked solution →Which of the following CANNOT carry sound?Read the answer and worked solution →An echo is a:Read the answer and worked solution →A whistle has a frequency of 1700 Hz. If the speed of sound in air is 340 m/s, the wavelength is:Read the answer and worked solution →A bat emits an ultrasonic pulse at 60 kHz. After 0.04 s, it hears the echo. How far is the obstacle? (Speed of sound = 340 m/s)Read the answer and worked solution →What is the TIME PERIOD of a sound wave with frequency 100 Hz?Read the answer and worked solution →Sound travels through a steel rail at 5000 m/s. A train signal sent through the rail reaches a distance of 1 km in:Read the answer and worked solution →A sound wave's loudness is perceived from its:Read the answer and worked solution →Sound levels above 80 dB sustained for long periods can:Read the answer and worked solution →The frequency of human hearing typically decreases with age. The MOST AFFECTED frequencies are:Read the answer and worked solution →The LOUDNESS of a sound depends on the wave's:Read the answer and worked solution →The audible range of frequency for humans is:Read the answer and worked solution →Reverberation refers to:Read the answer and worked solution →SONAR (SOund Navigation And Ranging) uses:Read the answer and worked solution →Which two animals are known to use natural echolocation to navigate and hunt?Read the answer and worked solution →CLASS9 · Physics · Sound — Spot the ErrorRead the answer and worked solution →Sound — true or false?Read the answer and worked solution →Compression or rarefaction?Read the answer and worked solution →True or false: soundRead the answer and worked solution →

Worked practice questions

Speed of sound in air is roughly:

  1. 340 m/s
  2. 3400 m/s
  3. 34 m/s
  4. Speed of light
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Correct answer: A. 340 m/s

At room temperature, sound travels at about 340 m/s in air. (Exact value depends on temperature — higher at warmer temperatures.) For comparison, speed in steel is ~5000 m/s; in water ~1500 m/s.

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How is sound INTENSITY related to the SQUARE of the AMPLITUDE?

  1. Independent
  2. Doubling amplitude doubles intensity
  3. Inversely
  4. Doubling amplitude makes intensity 4×
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Correct answer: D. Doubling amplitude makes intensity 4×

Intensity ∝ amplitude². If amplitude doubles, intensity becomes 4× (since 2² = 4). This is why doubling amplitude requires 4× the energy.

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Which of the following CANNOT carry sound?

  1. Steel (solid)
  2. Air (gas)
  3. Vacuum (no matter)
  4. Water (liquid)
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Correct answer: C. Vacuum (no matter)

Sound requires a medium with particles to vibrate. Vacuum has no particles, so sound can't propagate through it. Astronauts in space communicate via radio — electromagnetic waves don't need a medium.

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