MCQ : Sound - 1 Class 9 Science MCQs & solutions - Free

• Definition of Audible Range: The audible range of human hearing refers to the range of frequencies that can be heard by the average human ear.
• Upper Frequency Limit: The upper frequency limit of the audible range is typically around 20 kHz (20,000 Hz).
• Explanation:
  • As humans age, the ability to hear higher frequencies diminishes, with most adults unable to hear frequencies above 16 kHz or even lower.
  • Young children and some animals may be able to hear frequencies slightly higher than 20 kHz, but for the majority of the population, 20 kHz is considered the upper limit of human hearing.
• Options Analysis:
  • A: 20 kHz - correct answer. This falls within the typical upper limit of human hearing.
  • B: 2000 Hz - this frequency is much lower than the upper limit of human hearing.
  • C: 2 kHz - this frequency is also lower than the upper limit of human hearing.
  • D: 2,000,000 Hz - this frequency is extremely high and far beyond the upper limit of human hearing.
• Conclusion: The correct answer is A: 20 kHz, as this frequency falls within the typical upper limit of the audible range of human hearing.

• Option A: Sound waves - Transverse waves is incorrect because sound waves are mechanical and longitudinal waves, not transverse.
• Option B: Compression - Region of high pressure is correct. A compression is a region in a sound wave where particles are crowded together, resulting in high pressure.
• Option C: Rarefaction - Region of high pressure is incorrect because rarefaction is actually a region of low pressure where particles are spread apart.
• Option D: Medium for sound - Vacuum is incorrect because sound requires a medium (solid, liquid, or gas) to travel through. Sound cannot travel in a vacuum as there are no particles to propagate the wave.

The Assertion statement is correct as sound is indeed a form of energy that leads to the sensation of hearing in our ears.

The Reason statement is also correct as it accurately describes sound waves as longitudinal waves where particles move parallel to the direction of wave propagation.

However, the Reason does not directly explain the Assertion, so the correct answer is Option B.

In water, the particles are much closer together, and they can quickly transmit vibration energy from one particle to the next. This means that the sound wave travels over four times faster than it would in air, but it takes a lot of energy to start the vibration.

Absorptive material on the back and side walls will help reduce the reverberation time and unwanted reflections. If possible, try to avoid parallel surfaces, which can cause flutter echoes.

The speed of sound is calculated as the distance traveled by a point on a wave per unit time, which is defined as time.

The quality or timbre of sound is the characteristic that allows us to differentiate between sounds of the same pitch and loudness. It helps us perceive sounds as more pleasant or rich, such as tones, notes, music, or noise, based on their quality.

• Infrasonic waves: These are sound waves with frequencies below the lower limit of human hearing, which is typically regarded as 20 Hz.
• Frequencies: Infrasonic waves have frequencies below 20 Hz.

Sound waves are a type of wave characterised by the movement of particles within a medium. They are specifically known as mechanical waves because:

• They require a medium (such as air, water, or solid) to travel through.
• They cannot travel through a vacuum, unlike electromagnetic waves.
• Sound waves are produced by the vibrations of particles in the medium, transferring energy from one particle to another.

In summary, sound waves are distinct from electromagnetic and transverse waves, as they depend on particle interaction in a medium for propagation.

• Sound Propagation: Sound is a mechanical wave that requires a medium to propagate through. It cannot travel through a vacuum, which is why it cannot travel through space.
• Vacuum of Space: Space is mostly a vacuum, meaning it has very low density and pressure. Sound waves need particles to travel through, like air or water molecules, but in space, there are very few particles for the sound waves to interact with.
• No Medium: Without a medium for the sound waves to move through, they cannot transfer their energy from one point to another. This is why sound cannot travel through the vacuum of space.
• Other Media: In comparison, sound can travel through air, water, and solids like iron because these materials have particles that can carry the sound waves.