Question

A tuning fork vibrating at a frequency of 512 Hz is held over the top of a jar filled with water and fitted with a tap at the bottom. If the jar is 60 cm high and the speed of sound is 350 m/s, describe what occurs as the jar slowly emptied.

Answer 1

$$\lambda=\frac{v}{f}=\frac{350}{512}=0.684\ m$$

First resonance:

$$l_1=\frac{\lambda}{4}=\frac{0.684}{4}=0.17\ m=17\ cm$$

$$l_2=3\frac{\lambda}{4}=3\frac{0.684}{4}=0.51\ m=51\ cm$$

As the jar slowly emptied we can hear resonance when the height of the jar would be 17 cm and 51 cm.