The fundamental wavelength of a steel wire stretched taut between supports one meter apart is determined by the requirement that the wave has zero displacement at the fixed endpoints. The longest wavelength, or fundamental wavelength, for this setup is 2 meters, as it must have nodes at both ends. While some argue that a wavelength of 1 meter would require slack, it is clarified that a node can exist at the center of the wire without slack, provided the wire is under tension. The discussion also acknowledges that the wire can support higher frequency harmonics with shorter wavelengths. Understanding these principles is essential for analyzing the vibrational characteristics of the wire.