I understand why a person leads the congregation in prayer and studies Torah on his parent's yahrzeit (anniversary of death). This brings merit to the deceased by his or her descendant's continuing to do mitzvot in this world. My question is how, and if, lighting a candle accomplishes this goal? Thank you.
The soul, or neshamah, of the departed derives joy from the kindling of lights. This enjoyment brings the neshamah to a state of spiritual expansion. The neshamah itself is a portion of light drawn from the light of the intellect (sechel). In Proverbs, King Solomon refers to this when he writes, "Man's soul is G-d's candle."
Therefore every year on the anniversary of the passing of one's parent, or other relatives, one kindles a light, called the yahrzeit candle; for on this day, the neshamah has permission to travel about in the world. It comes and sees the light burning for it, and receives spiritual satisfaction from this.
Some authorities write that it's best to light the yartzeit candle in the synagogue. Perhaps this brings merit to the deceased by enhancing the honor and ambiance of the synagogue.
- Elef Hamagen, Sha'ar 3, cited in "Mourning in Halacha" by Rabbi Chaim Binyamin Goldberg