Question

Complete the following sentence.
Sound cannot travel through ……………, but it requires a …………. .
A. Air, medium
B. Water, medium
C. Solids, medium
D. Vacuum, medium

Answer 1

Hint: Sound wave is a pressure wave means it travels in the medium by compressing and then lengthening the consecutive particles in the medium. Denser the medium, faster the speed of sound.

Complete answer:
We know that sound waves are in the form of longitudinal waves since the particles in the medium travel parallel to the propagation of the wave. Sounds can be produced by vibrating bodies such as tuning forks, strings of guitar. Humans produce sound by vibrating the vocal cords.

Sound cannot travel through vacuum since the vacuum is not a material medium. Sound requires a material medium for its propagation. To answer why the sound cannot propagate through vacuum first of all, let’s answer how the sound travels through the air. Sound wave is a pressure wave means it travels in the medium by compressing and then lengthening the consecutive particles in the medium. Denser the medium, faster the speed of sound since there are comparatively more number of particles to interact. In a vacuum, there are no such particles or molecules which can be compressed by the vibrating sound wave. Therefore, we can see that the sound wave does not propagate through the vacuum.

We can see the real life example of the fact that the sound wave travels faster in denser mediums like steel, water, etc when the train blowing a continuous horn passes above the bridge of the river. The listener stands at the edge of the river at a distance of let’s say 3 kilometer from the bridge along the river. He is still able to hear the horn of the train since the sound travels faster in the water than in the air.

Therefore, the correct answer is option (D).

Note:Students can answer this question referring to the fact that the sound wave is a mechanical wave. The mechanical waves require material medium for their propagation. Vacuum is not the material medium. Therefore, the sound wave cannot travel through the vacuum.