Answer:
20 (1/m)
Explanation:
Hi there!
The wavenumber k is related to the wavelength λ as:
k = 2π/λ
It appears in wave equations as the argument of the sine or cosine functions and is multiplied by a distance.
In the given equation, if the distance is x, the number 20 must have dimentions of 1/D (D == distance) which are the dimentions of the wavenumber, if considering SI units, the units of x must be meters, therefore, the units of the wavenumber must be 1/meters
The wavenumber must be: 20 (1/m)
