Sound Waves: 19 MCQs with answers

Vibrations of a body

Sound is produced when a body vibrates, as demonstrated by experiments with a rubber string, wire, and tuning fork.

Longitudinal waves

In air, sound travels as longitudinal waves where particles vibrate about their mean positions in the direction of propagation.

Vacuum

Sound requires a material medium; it cannot travel in vacuum because there are no particles to vibrate and transmit the disturbance.

Blanket

Blankets and thick curtains absorb most of the sound incident on them, transmitting or reflecting only a small fraction.

V = fλ

The fundamental wave relation is V = fλ, where V is velocity, f is frequency, and λ is wavelength.

High pressure

A compression is a region where particles are closer together, resulting in high pressure.

A region of low pressure

A rarefaction is a region where particles are spread out, resulting in low pressure.

340 m/s

The speed of sound in air is about 340 m/s, much slower than the speed of light.

False

Sound requires a material medium; it cannot travel through vacuum because there are no particles to vibrate.

False

Light travels much faster than sound; in air, light travels at about 3 × 10^8 m/s, while sound travels at about 340 m/s.

340 m/s

Using V = fλ, V = 500 × 0.68 = 340 m/s.

Iron

Sound travels faster in solids like iron than in liquids or gases because particles are closer and transmit disturbances more quickly.

20,000 Hz

Ultrasonic frequencies are above 20,000 Hz, which is the upper limit of human hearing.

Lightning is seen before thunder is heard

Light travels much faster than sound, so lightning is seen almost instantly while thunder takes time to reach us.

Sonar

Ultrasonic waves are used in sonar for navigation and detection of objects underwater.

Nature of the medium

The speed of sound depends on the properties of the medium (e.g., density, elasticity), not on the wave's frequency or amplitude.

Sound waves carry mechanical energy

Sound waves are mechanical waves that carry mechanical energy from vibrating particles to produce hearing sensation.

0.001 s

Time period T = 1/f, so T = 1/1000 = 0.001 s.

Ultrasonic refers to high frequency, supersonic refers to high speed

Ultrasonic refers to frequencies above 20,000 Hz, while supersonic refers to speeds greater than the speed of sound.