Final answer:
Coulomb's law states that the electrostatic force between charges is inversely proportional to the square distance between them. So the correct option is a.
Step-by-step explanation:
Coulomb's law states that the force of attraction or repulsion between electric charges is inversely proportional to the square of the distance between them. This law is exemplified by the equation F = k(q₁q₂/r²), where F is the electrostatic force between two point charges, q₁, and q₂ are the amounts of the charges, r is the distance between the centers of the two charges, and k is Coulomb's constant. Coulomb's law is a cornerstone in the study of electrostatics and demonstrates that if the distance between two charges is doubled, the electrostatic force reduces by a factor of four (2²).
Additionally, while Newton's law of universal gravitation follows an inverse-square relationship and might seem similar to Coulomb's law, they operate on different constants and deal with different forces (gravitational vs. electrostatic). Furthermore, while gravity only produces attraction between masses, the electrostatic force can result in either attraction or repulsion between charges.
Therefore, the correct answer is a. Coulomb's law.