In an experiment with a convex lens, The plot of the image distance (v^′) against the object distance (μ^′) measured from the focus gives a curve v^′…

In an experiment with a convex lens, The plot of the image distance $\displaystyle \left(v^{\prime}\right)$ against the object distance $\displaystyle \left(\mu^{\prime}\right)$ measured from the focus gives a curve $\displaystyle v^{\prime} \mu^{\prime}=225$. If all the distances are measured in cm. The magnitude of the focal length of the lens is \_\_\_\_ cm.