Concept:The sharp point of an uncharged conductor can discharge a charged electroscope by ionising the surrounding air.
Explanation:When the pointed end of the uncharged optical pin is brought near the positively charged cap of the electroscope, it becomes charged by induction.
The induced opposite charge concentrates at the sharp point, creating a very strong electric field.
This strong field ionises the nearby air molecules.
The ions gradually neutralise the positive charge on the electroscope.
As the charge decreases, the gold leaf loses its divergence and slowly falls back.
Hence, the gold leaf is observed to collapse slowly.
Answer:A. collapse slowly