explain why ahmadabad and kolkata are able to se the noon sun exactly overhead in a year but not in delhi.
Ahmadabad and Kolkata lie within the tropical zone and Delhi slightly above the Tropic of Cancer. The the two former cities get the overhead sun twice a year This happens once when the Suns direct rays shifts from the equator to the Tropic and secondly when it moves away from the Tropic to the Equator. However, the overhead Sun never over the areas like Delhi that does not fall within the Tropical Zone.