What is the significance of the three scenes which take place upon the scaffold?

The significance particularly involves Dimmesdale. In the first scene on the scaffold he acts as Hester's accuser. He is bathing in his own sin and guilt here. In the second scene he tries so hard to cleanse himself. The agony of his lie is killing him yet his fear is stronger. The last scene is one of atonement. Dimmesdale finally comes clean of his sin and guilt.