Question

Describe what you believe to be the similarities and differences between a standing wave in a string and a sound wave.

Answer 1

Standing Waves - These are waves which are produced when two travelling waves propagating in opposite directions but along the same line, with equal velocities super-impose with each other. In such cases, the resultant wave does not travel in any direction but remains stationary between two fixed boundaries. Standing wave formation is valid in the case of both transverse and longitudinal waves.

Differences:

1. When the transverse waves on a string are allowed to act between two boundaries, they form transverse standing waves. But sound waves are longitudinal waves. So in between fixed boundaries they form longitudinal standing waves.
2. For, standing waves on string, important example is musical instrument like sitar. Here the boundaries are fixed. While in case of sound waves, an important example is instrument like organ pipe. Here the waves can exist when both the ends of the air column are closed or both are open or even when one is closed and one is open.
3. Standing waves on a string are not pressure waves and while sound standing waves are pressure waves.

Similarities:

1. Both are mechanical waves or in other words, requires a material medium to exist and the wave velocities depend on the properties of the medium.
2. Both of these waves are confined to a small region of the medium and does not travel. Also, since they are not travelling, they does not transmit energy to the medium.
3. Both leads to formation of different harmonics of vibrations.