A tuning fork of frequency 558 Hz is placed near the top of the pipe shown in the Figure. The water level is lowered so that the length L slowly increases from an initial value of 20.0 cm. Determine the next two values of L that correspond to resonant modes. (Assume that the speed of sound in air is 343 m/s.)

I found the wavelenght:
0.2m x 4 = 0.8m. Then used the wavelength to calculate the other lengths: L3 = [3(.8)/4] x (343/558). This was incorrect. What am I doing wrong?

The wavelength of the sound is
(sound speed)/(frequency)

Resonances of an open pipe occur when the pipe length is an odd number of quarter wavelengths.

2 answers

l=lambda/4
456