Final answer:
When the charge q is doubled, the final electric field strength ef is twice as strong as the initial electric field strength ei, resulting in a ratio ef/ei of 2:1.
Step-by-step explanation:
The electric field (E) created by a point charge (q) at a distance (r) is given by Coulomb's law, which states that E = k * q / r^2, where k is Coulomb's constant.
If the charge q is doubled to become 2q, the new electric field strength ef at the same distance will be Ef = k * (2q) / r^2.
This means that the final electric field strength will be twice as strong as the initial electric field strength because Ef = 2 * (k * q / r^2) = 2 * Ei.
Therefore, the ratio ef/ei of the final electric field strength to the initial electric field strength when q is doubled is 2:1.