The solution at revision #20335 of , by Tete. This is not the current version.
← Older Newer → Changes Current version

Statement

3.9.16. Let's bring a vibrating tuning fork to a high cylindrical vessel, in which water is poured little by little. We will hear the sound getting stronger, weaker and stronger again. How to explain this? Why does the tuning fork sound weak without the vessel?

For problem $3.9.16$

Solution

For problem $3.9.16$
For problem

The sound gets stronger when the air column in the vessel above the water has length that permits a standing wave, i.e. , where is the speed of sound and is the frequency of the tuning fork. In between, the sound gets weaker. The figure shows standing waves of displacement waves, which must have antinodes at the opening of the vessel and nodes at water surface. (The fact that the standing waves fit the width of the vessel is for an esthetic not physical reason.)

Answer

See the solution.