Question

A tuning fork vibrating at a frequency of 512 Hz is held on 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

Calculate the wavelength:

$$\lambda=\frac{v}{f}=0.684\text{ m}.$$

As the jar is emptied, the first resonance will occur at

$$L_1=\frac{1}{4}\lambda=0.171\text{ m},$$

the second will occur at

$$L_1=\frac{3}{4}\lambda=0.513\text{ m}.$$