Under what tension should be a guitar string (with length 64.5 cm and linear mass density 0.1 g/cm), so that its first harmonic sounds at 120 Hz? The tension in the string, t = Units Select an answer v What are the frequencies and wavelengths of the 2nd and 3rd harmonics? The frequency of 2nd harmonic, f = Units Select an answer . The wavelength of 2nd harmonic, = Units Select an answer The frequency of 3rd harmonic, f3 = Units Select an answer The wavelength of 3rd harmonic, ^3 = Units Select an answer