What does Hawthorne intend by including the imagery of sunlight/shadows?

Sunlight returns once more in Chapter 16, as Hester tries to catch a beam of sunlight for Pearl. Earlier in the novel, Hester stated that she could never offer Pearl sunlight—she had no more for her child. But now she has come full circle, enough to want to give her child light, and even enough to want to show off her child in an approving light. Yet, she cannot catch the light; the child is still without a true father. Pearl is still not at peace. At the same time, we see that Hester, by confessing and taking responsibility for her sin, has been able to heal.