The correct option is (a).
Explanation
A candle flame consists of three distinct zones based on the availability of oxygen and the degree of combustion: the innermost zone (dark zone), the middle zone (luminous zone), and the outer zone (non-luminous zone).
Statement-wise Analysis
- Statement 1 is Correct: The dark zone is the innermost zone of the flame that directly surrounds the wick. It appears black because it contains unburnt wax vapours.
- Statement 2 is Incorrect: This zone is characterized by the absence of combustion due to the lack of oxygen supply in the innermost region. Complete combustion of wax vapours occurs in the outermost (non-luminous) zone, where oxygen is plentiful.
- Statement 3 is Incorrect: The dark zone is the least hot part of the flame because no combustion takes place there. The hottest part of the flame is the outer zone, where complete combustion generates the maximum heat.
Key Takeaway
The dark zone (innermost) contains unburnt vapours and is the coolest region; the luminous zone (middle) involves partial combustion (yellow flame); and the non-luminous zone (outer) involves complete combustion (blue flame) and is the hottest region.