I have always read the light as being representative of love and caring for others. Remember how Scrooge is bothered by it and requests the spirit to pull his cap down on his head further so the light would be extinguished? The spirit becomes upset and offended, but at this point in Scrooge's "growth", he is not yet ready to open up completely to the love and emotions that come with having friends and family surround you during the holidays. He is ready to squash it or "turn it out" as he has done in his earthly life so far. This is why the spirit becomes so upset and angry with him...one, the spirit wants to bask in that light (it is beautiful and warm), and two, Scrooge isn't learning much when he continues along the same path he has always traveled.
Light is a common symbol in literature, often used to represent enlightenment or knowledge. While it certainly can also have all of the meanings listed in the pervious answers, it might also represent Ebenezer Scrooge moving from ignorance to knowledge.
At the beginning of the book, Ebenezer is lacking empathy for others, but he also seems genuinely unaware of their lives. He asks Fred why he got married. He asks if the work houses are still open. He is not aware that Tiny Tim is crippled. In so many ways he really is ignorant of those around him.
As the story continues, Scrooge begins to literally and figuratively "see the light." He learns more about those around him, becomes more aware of his own actions, and changes as a result. He changes because he has been enlightened.
In Stave I of Charles Dickens’ A Christmas Carol, Ebenzer Scrooge is visted by the ghost of Jacob Marley, his now-deceased former business partner who has appeared before the miserly, bitter old man to warn him of the perils to come unless he changes his ways. It is, of course, the Christmas season, and the story of the birth of Jesus hangs in the air as a reminder of the season’s true meaning. The ghost of Jacob Marley rhetorically inquires of himself and of Scrooge the reason he let so many holy seasons pass without acknowledging those around him:
“At this time of the rolling year,” the spectre said, “I suffer most. Why did I walk through crowds of fellow-beings with my eyes turned down, and never raise them to that blessed Star which led the Wise Men to a poor abode! Were there no poor homes to which its light would have conducted me!”
In Stave II, after the ghost of Marley has warned Scrooge and informed him that he would be visited by three spirits, the old man waits anxiously in his bed. At the prescribed time, the first of the three spirits announces itself:
“He spoke before the hour bell sounded, which it now did with a deep, dull, hollow, melancholy ONE. Light flashed up in the room upon the instant, and the curtains of his bed were drawn.”
Interpretations of the meaning of the light can vary, but, in the context of Marley’s acknowledgment of the true meaning of the season, and in the context of Scrooge’s imminent moral awakening, it is possible that the light represents both the “blessed Star” and the moment Scrooge’s transcendental transformation from “scrooge” to jovial, benevolent pillar of the community.
We are currently reading the book and my Pre-AP reading teacher said that the light symbolizes truth...Hope this helps:)