The Wilson cloud chamber is based on the principle that supersaturated vapours condensemore easily onI. ionsII. moleculesIII. nuclear dust particles

Explanation

The correct answer is I only. The Wilson cloud chamber operates on the principle that supersaturated vapours condense more easily on ions. These ions provide the necessary nuclei for condensation, allowing the formation of visible cloud tracks that indicate the paths of charged particles. Option II is incorrect because molecules, while they can sometimes act as nucleation sites, are not the primary mechanism utilized in the Wilson cloud chamber. Option III is incorrect because nuclear dust particles are not involved in the typical operation of a Wilson cloud chamber in the condensation process. Therefore, the presence of ions is the critical factor in this context.