Question

Give reasonns:goldsmiths use the non-luminous zone of the flame.

Answer 1

The non-luminous zone of the flame produces the most heat. Goldsmith's have to shape the gold to make ornaments ,etc out of it. To achieve this the goldsmith needs a lot of heat, this heat is acquired by the non-luminous zone of the flame as highest heat is dissipated in the non-luminous zone. So the goldsmith uses the non-luminous zone of the flame to maximize the use of the fuel used.