Ray Optics

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

Integer / Numeric Answer Type

Enter your answer as a number (integer or decimal).