Final answer:
The three longest wavelengths for standing soundwaves in a 122-cm-long tube can be found using the formula 4L/n.
Step-by-step explanation:
The three longest wavelengths for standing soundwaves in a 122-cm-long tube can be found by using the formula 4L/n, where L is the length of the tube and n is the harmonic number. For the first harmonic (fundamental frequency), n = 1, so the wavelength would be 4 * 122 cm. For the second harmonic (first overtone), n = 2, so the wavelength would be 4 * 122 cm / 2. And for the third harmonic (second overtone), n = 3, so the wavelength would be 4 * 122 cm / 3.