Question

An unlit incens stick gives smell only when we come close to it but on lighting the stick we get smell even far away from it , why?

Answer 1

Because, after the incense stick is lightened the smell is carried out by means of air to us.
 While it is lightened it produces a sort of smoke which is carried by the air to our nostril.
But , when it is not lighten it does not produce any smoke which can not be carried by the air to a far distance.

Hope my answer helps you.....