A lightning rod with sharp tip reduces damage risk. Which one of...

A lightning rod has a sharp tip, which means the radius of curvature at the tip is very small.

Since surface charge density $\sigma$ is inversely proportional to the radius of curvature, the charge density at the sharp tip becomes very high.

The electric field near the surface of a conductor is given by $E = \dfrac{\sigma}{\epsilon_0}$. Thus, the intense charge density creates a very strong local electric field.

This strong electric field ionizes the surrounding air molecules, leading to a continuous corona discharge. This discharge helps in partially neutralizing the charge of the cloud and provides a conducting path for the lightning to safely reach the ground, thereby reducing the risk of damage.

Answer: It enhances field and promotes continuous corona discharge.