Question

A loudspeaker is placed so that it is in contact with side-by-side regions of air, water, and iron, as shown in the diagram below. The loudspeaker is connected to a tone generator that is turned on and plays a note with a frequency of 200 Hz. In which material would the 200 Hz sound wave have the longest wavelength? In which would it be shortest? Using the simulator ‘Grayscale’ representation, shade in the boxes in the diagram above to show how the wavelength of the 200 Hz sound wave would be different in each of these materials. Explain your reasoning.

Answer 1

So whenever there is a change in a medium we have the velocity of sound changing. But now that the frequency never changes at any circumstances. The frequency of sound is always a property of the source and cannot be changed. Thus if the velocity is changing but the frequency is constant then what is the property that's changing? It is the wavelength that changes. Always the velocity of sound is directly proportional to the density of the medium. This is because if the density is more then the material is more tightly packed and thus easy for atoms to transmit the vibration to its neighbors.

So since velocity is directly proportional to wavelength then even wavelength is directly proportional to the density of the medium.

since

it is obvious that: