Answer:
The speaker uses repetition in the phrase "lamp light gloated o'er" and "lamp light gloating o'er" in order to emphasize that the light is next to the chair where the speaker is sitting, which contributes to a sad mood.
Step-by-step explanation:
Repetition creates a structure in the poem and helps to emphasize the importance of a symbol in the text. By insisting on a particular element, the poet helps the reader to notice and focus on a specific motif or emotion that the author wants to highlight.