Consider the figure showing different zones of the candle flame.

                                        

Which statement is true about these zones?

The candle flame has ‘3’ different zones

i) The outer zone: Non luminous zone and produce heat $\to$ Flame blue in colour

ii) The middle zone: Luminous zone produce less heat and light $\to$  Flame Yellow in colour

The yellow colour of the flame is due to incomplete burning of carbon particle

iii) The inner zone: Black in colour (dark zone)$\to$ No combustion

Znoe I is used for melting of gold – hottest zone.