Sound cannot travel in which of the following mediums?

Correct option is B

The correct answer is (b) Vacuum

Explanation:

• Sound is a mechanical wave, which means it requires a material medium (solid, liquid, or gas) to propagate.

• It travels through a medium by causing the particles of that medium to vibrate; these vibrations are passed from one particle to the next.

• In a vacuum, there are no atoms or molecules to vibrate and carry the sound energy, which is why sound cannot travel through it.

• According to NCERT Class 9 Science (Sound), sound waves are longitudinal waves that create regions of compression and rarefaction in a medium.

• Because space is largely a vacuum, astronauts must use radio waves (which are electromagnetic and do not require a medium) to communicate.

Information Booster:

• The speed of sound depends on the properties of the medium through which it travels, specifically its density and elasticity.

• Sound travels fastest in solids (like metal) and slowest in gases, because particles in solids are packed more closely together, allowing for quicker transfer of vibrations.

Additional Knowledge:

Gas (Option a)

• Sound travels through gases like air by the vibration of air molecules.

• At $0^{\circ}C$, the speed of sound in air is approximately 331 m/s.

Fluid (Option c)

• Fluids (liquids and gases) allow sound to propagate; for example, sound travels about 4.3 times faster in water than in air.

• Marine animals like whales and dolphins rely on sound traveling through water for communication.

Metal (Option d)

• Metals are solids, and sound travels exceptionally well through them.

• For instance, the speed of sound in steel is about 5960 m/s, which is much higher than in air or water.