The correct option is (c).
Explanation
A candle flame consists of three distinct zones based on the availability of oxygen and the extent of combustion: the innermost zone (dark), the middle zone (luminous), and the outer zone (non-luminous). Each zone varies in temperature and composition.
Statement-wise Analysis:
- Statement 1 is Incorrect. The innermost zone (dark zone) around the wick consists of unburnt wax vapours. No combustion takes place here due to the lack of oxygen. Consequently, it is the least hot part of the flame, not the zone of complete combustion.
- Statement 2 is Correct. The middle zone is the luminous zone where the oxygen supply is insufficient for complete burning. This leads to partial combustion of wax vapours. The unburnt carbon particles glow, giving the flame its characteristic yellow colour.
- Statement 3 is Correct. The outer zone is the non-luminous zone (faintly blue). Here, the oxygen supply is ample, allowing for complete combustion of the fuel. This zone releases the maximum amount of energy, making it the hottest part of the flame.
Key Takeaway:
The outer zone (blue) represents complete combustion and is the hottest; the middle zone (yellow) represents partial combustion; and the innermost zone (black) contains unburnt vapours and is the least hot.