The wave speed $v$ in deep water is related by $v^2 = \dfrac{g\lambda}{2\pi}$ in which $\lambda$ represents the wavelength of the waves and $g$ denotes the acceleration of free fall. A student records the wavelength $\lambda$ and the frequency $f$ for several of these waves. Which graph ought he to plot so that the result is a straight line passing through the origin?
- A$f^2$ against $\lambda$
- B$f$ against $\lambda^2$
- C$f$ against $\dfrac{1}{\lambda}$
- D$f^2$ against $\dfrac{1}{\lambda}$