## Essential University Physics: Volume 1 (3rd Edition)

We can find the ratio of diameters as follows: $ratio=\frac{D_{hydrogen}}{D_{proton}}$ $ratio=\frac{0.1nm}{1fm}=\frac{0.1\times 10^{-9}m}{1\times 10^{-15}m}=1\times 10^5$