The force between two point electric charges kept at a distance d apart in air is F. If these charges are kept at the sme distance in water, the force between the charges is F'. The ratio `F'//F` is equal to ……….. .

Explanation

To solve the problem, we need to find the ratio \( \frac{F'}{F} \) where \( F \) is the force between two point electric charges in air, and \( F' \) is the force between the same charges when they are placed in water.

### Step-by-Step Solution:

1. **Understanding Coulomb's Law**:
The force \( F \) between two point charges \( q_1 \) and \( q_2 \) separated by a distance \( d \) in air is given by Coulomb's law:
\[
F = \frac{k \cdot q_1 \cdot q_2}{d^2}
...