Question

Sound waves cannot travel in
A. Air
B. Metal
C. Vacuum
D. Water
E. Wood

Answer 1

Hint: Here, sound waves require some medium to travel like solid, liquid or gas state. So, from this we can differentiate the given option in these three categories and the remaining option which does not satisfy in the category is the answer.

Complete Step-by-Step solution:
Sound is the mechanical wave that is produced by vibration of particles of the medium through which sound is moving. If sound is moving from left to right through air, then particles of the medium i.e. air will be displaced both right side and left side as energy of the sound passes through it.
The motion of the particles is parallel to the direction of the energy transport. Now, sound waves require mediums such as solid, liquid or gas. We know that molecules of solid are tightly packed. Liquids are not as tightly packed compared to solid. And gas molecules are more loosely packed than solids and liquids. Sound travels about four times faster and farther in water than air because the spacing of the molecules enables sound to travel much faster through liquid than gas.
So, sound waves are travelling vibrations of particles in media such as air, water, wood or metal. Thus, they cannot travel through empty space where there are no atoms or molecules to vibrate.
So, in the option we can see that except the vacuum option, all the options are classified into either solid, liquid or gas state but in vacuum there is no air or any other gas present. Thus, sound waves cannot travel in vacuum.
Hence, option (c) is the correct answer.

Note: Students sometimes make mistakes in understanding the difference between vacuum form and gas form. So, to be very clear that Vacuum is like an empty room where there is no air, sunlight and water so sound cannot go outside the room. While air is the best example of gas form through which we are able to talk with one another in daily life. So, don’t make this mistake.