Final answer:
The fundamental frequency, or first harmonic, is the lowest resonant frequency of a system and determines all higher multiples known as harmonics. For a string, it's calculated as f1 = Vw/2L and can be altered by changing the tension, which affects the wave speed.
Step-by-step explanation:
The fundamental frequency, also known as the first harmonic, corresponds to the lowest frequency at which a system resonates. In the case of a vibrating string, the fundamental frequency is determined by the equation f1 = Vw/2L, where Vw represents the wave speed and L the length of the string. This frequency creates the longest wavelength and establishes the basis for all other frequencies, which are known as overtones or harmonics. Each harmonic is a multiple of the fundamental frequency, meaning the first overtone is the second harmonic (twice the fundamental frequency), the second overtone is the third harmonic (three times the fundamental frequency), and so on. Adjusting the tension in the string changes these harmonics as the wave speed Vw changes accordingly.