Sound

Sound waves cannot travel through a

[amp_mcq option1=”copper wire placed in air” option2=”silver slab placed in air” option3=”glass prism placed in water” option4=”wooden hollow pipe placed in vacuum” correct=”option4″]

Sound waves are mechanical waves, meaning they require a medium to propagate. They travel through the vibrations of particles in solids, liquids, and gases. A vacuum is a space essentially devoid of matter. Therefore, sound waves cannot travel through a vacuum because there are no particles to transmit the vibrations. A wooden hollow pipe placed in vacuum includes a region (the vacuum surrounding and possibly inside the pipe) through which sound cannot travel.

– Sound propagation requires a material medium (solid, liquid, or gas).
– Sound travels at different speeds in different media (typically fastest in solids, slower in liquids, and slowest in gases).
– Vacuum has negligible matter, so it cannot support the propagation of mechanical waves like sound.

Options A, B, and C describe scenarios where sound can travel through solid materials (copper wire, silver slab, glass prism) and/or gaseous air or liquid water. In a vacuum, even if a solid object like a wooden pipe is present, sound cannot travel *through* the vacuum space itself. If sound were generated within the solid pipe, it could travel through the pipe material, but it would not propagate outward into the vacuum. The question asks where sound cannot travel *through*, and the presence of vacuum prevents propagation across that space.

A person rings a metallic bell near a strong concrete wall. He hears the echo after 0.3 s. If the sound moves with a speed of 340 m/s, how far is the wall from him?

[amp_mcq option1=”102 m” option2=”11 m” option3=”51 m” option4=”30 m” correct=”option3″]

The sound travels from the person to the wall and then reflects back to the person as an echo. The total distance covered by the sound is twice the distance between the person and the wall. The time taken for this round trip is 0.3 seconds, and the speed of sound is 340 m/s.
Total distance = Speed × Time
Total distance = 340 m/s × 0.3 s = 102 meters.
The distance to the wall is half of the total distance.
Distance to wall = Total distance / 2 = 102 m / 2 = 51 meters.

An echo involves sound travelling to a surface and back, so the distance to the surface is half the total distance covered by the sound.

The speed of sound in air is approximately 343 m/s at 20°C, but it varies with temperature and humidity. The value 340 m/s used in the problem is a typical approximation.

Which one of the following statements is not correct?

[amp_mcq option1=”Sound waves in gases are longitudinal in nature” option2=”Sound waves having frequency below 20 Hz are known as ultrasonic waves” option3=”Sound waves having higher amplitudes are louder” option4=”Sound waves with high audible frequencies are sharp” correct=”option2″]

Let’s evaluate each statement:
A) Sound waves in gases are longitudinal in nature: Correct. Sound waves in fluids (gases and liquids) are longitudinal, meaning the particles of the medium vibrate parallel to the direction of wave propagation.
B) Sound waves having frequency below 20 Hz are known as ultrasonic waves: Incorrect. Frequencies below the normal human hearing range (approximately 20 Hz) are called infrasonic waves. Ultrasonic waves are sound waves with frequencies above the normal human hearing range (approximately 20 kHz).
C) Sound waves having higher amplitudes are louder: Correct. The amplitude of a sound wave is related to its intensity, and intensity is perceived as loudness. A higher amplitude corresponds to higher intensity and thus a louder sound.
D) Sound waves with high audible frequencies are sharp: Correct. Frequency corresponds to pitch. Higher frequency means higher pitch, and sounds with high pitch are often described as sharp or shrill.
The statement that is NOT correct is B.

Sound frequencies below the audible range (20 Hz) are infrasonic, and frequencies above the audible range (20 kHz) are ultrasonic.

The audible range for humans is typically considered to be from 20 Hz to 20 kHz, although this range can vary individually and decreases with age.

Which one of the following statements is correct ? The velocity of sound :

[amp_mcq option1=”does not depend upon the nature of media” option2=”is maximum in gases and minimum in liquids” option3=”is maximum in solids and minimum in liquids” option4=”is maximum in solids and minimum in gases” correct=”option4″]

The velocity of sound depends on the properties of the medium through which it travels, particularly its elasticity and density. Sound travels fastest in solids because the particles are closely packed and interactions are strong, allowing vibrations to propagate quickly. It travels slower in liquids and slowest in gases, where particles are farther apart and interactions are weaker. Thus, the velocity of sound is maximum in solids and minimum in gases.

Sound travels fastest in solids, slower in liquids, and slowest in gases.

Factors like temperature also affect the speed of sound within a given medium. For example, the speed of sound in air increases with temperature. However, the general ranking of speeds in solids, liquids, and gases holds true under typical conditions.