Waves and Sound Quiz

Grade 9 · Science · Quiz

Test your understanding of wave properties, sound, and wave behavior with 10 questions.

Questions

  1. Which property of a sound wave determines its pitch?

    1. Amplitude
    2. Wavelength
    3. Frequency
    4. Speed
    Show answer

    Answer: Frequency

    Frequency determines pitch — high frequency = high pitch (e.g., a flute), low frequency = low pitch (e.g., a tuba). Amplitude determines loudness.

  2. Light is a longitudinal wave.

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    Answer: False

    Light is a transverse electromagnetic wave that can travel through a vacuum. Sound is the classic longitudinal wave.

  3. A wave with a wavelength of 2 m and speed of 340 m/s has a frequency of:

    1. 170 Hz
    2. 342 Hz
    3. 680 Hz
    4. 338 Hz
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    Answer: 170 Hz

    f = v/λ = 340 m/s ÷ 2 m = 170 Hz. Use the wave speed formula v = fλ and rearrange to solve for frequency.

  4. The distance from one crest to the next on a wave is called the ___.

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    Answer: wavelength

    Wavelength (λ) is measured from any point on one wave cycle to the identical point on the next — crest to crest, trough to trough, or compression to compression.

  5. In which medium does sound travel fastest?

    1. Air
    2. Water
    3. Steel
    4. Vacuum
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    Answer: Steel

    Sound travels faster in denser, more rigid materials. Speed in steel (~5,100 m/s) >> water (~1,480 m/s) >> air (~343 m/s). It cannot travel in a vacuum.

  6. Increasing a wave's amplitude increases its energy.

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    Answer: True

    Energy carried by a wave is proportional to the square of its amplitude. Double the amplitude, quadruple the energy.

  7. Which best describes a compression in a longitudinal wave?

    1. A region where particles are far apart
    2. A crest in the wave
    3. A region where particles are close together
    4. The wave's maximum height
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    Answer: A region where particles are close together

    Compressions are high-pressure, high-density regions in a longitudinal wave where particles bunch together. Rarefactions are low-pressure, low-density regions.

  8. Sound is measured in units called ___.

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    Answer: decibels

    Decibels (dB) measure sound intensity on a logarithmic scale. 0 dB is the threshold of human hearing; 120 dB is the pain threshold; 60 dB is normal conversation.

  9. The Doppler effect occurs when:

    1. A wave reflects off a surface
    2. The source or observer is moving
    3. Amplitude increases suddenly
    4. Two waves interfere
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    Answer: The source or observer is moving

    Relative motion between source and observer compresses or stretches the perceived wave, changing its apparent frequency — the Doppler effect.

  10. Which type of wave can travel through empty space?

    1. Sound waves
    2. Longitudinal waves
    3. Seismic waves
    4. Electromagnetic waves
    Show answer

    Answer: Electromagnetic waves

    Electromagnetic waves (light, radio, X-rays) are self-propagating and need no medium. All other options require a medium to transfer energy.

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