Question

Why is circular blackish ring is formed on the glass plate when it is bought near the candle flame

Answer 1

Answer:

Here's your answer mate

Explanation:

The color changes, and movement of the flame can be hypnotic. Blackened glass obscures this interplay and interrupts your visual enjoyment. A blackened glass fireplace door is usually the result of soot buildup, indicating that the fuel being used in the fireplace is not burning completely.

Answer 2

A circular blackish ring is formed on the glass plate/slide. It indicates the deposition of unburnt carbon particles present in the luminous zone of the flame.

Hope it helps u :D