Physics Study Guide/Standing waves
Standing waves edit
Wave speed is equal to the square root of tension divided by the linear density of the string.
μ = m/L

Linear density of the string is equal to the mass divided by the length of the string.
λ_{max} = 2L

The fundamental wavelength is equal to two times the length of the string.
Variables
λ: wavelength (m) 
Definition of terms
Tension (F): (not frequency) in the string (t is used for time in these equations). Units: newtons (N) 
Fundamental frequency: the frequency when the wavelength is the longest allowed, this gives us the lowest sound that we can get from the system.
In a string, the length of the string is half of the largest wavelength that can create a standing wave, called its fundamental wavelength.