Question

In which of the three media air, water or iron, does sound travel the fastest at a particular temperature?

Answer 1

Find out the medium which is the densest as temperature is the same in all these media. Compare the densities of air, water and iron. Sound travels fast in the medium which is the densest.

Complete answer:
Speed of the sound is the distance travelled by a sound wave, as it propagates across an elastic medium, per unit time. Recall that sound is a kinetic energy signal which is transferred from one particle to another particle. So unlike light which is an electromagnetic radiation the speed of light depends on various factors such as the physical properties of the medium.

We can see that the closest the particles are to each other, the less is the time needed to transmit the sound energy and with increase in the strength of the bonds between them, the time required further reduces. Now if the time reduces the more the distance that the sound wave can travel in a unit time, so the speed increases if the time taken for the propagation of the wave reduces.

So, with increase in the density of the medium, which indicates the number of particles in a unit area or in other words it describes how closely the particles are packed, the speed of the sound is expected to increase.From the above discussion, we can see that the speed of sound is greater in solids than in liquids and is lesser in case of gases because of their decreasing densities. In the question we are given the media air – gaseous state, water – a liquid and iron – a solid. So, the speed of sound will be greater in iron as it is the densest.

Hence, among the three media air, water or iron sound travels fastest in iron at a particular temperature.

Note: Remember that temperature also affects the speed of sound. The higher is the temperature the more excited are the particles and so the transfer of energy is faster and faster is the propagation of sound.