What is the effect on everyone when he wears his black veil

When the minister, Parson Hooper, appears at the meeting house wearing a black veil over his face, his parishioners experience a number of effects. Firstly, Goodman Gray wonders if it really is Parson Hooper because he cannot see the minister's face.
Secondly, the parishioners, who are waiting on the steps, are described as "being wonder-stuck." They are so dumbfounded by his veil that many of them do not even greet the parson when he speaks to them.
Thirdly, for some members of the congregation, the black veil puts them ill at ease. One woman, described as having "delicate nerves," leaves the meeting house. Others are described as being "pale-faced," meaning that the veil makes them feel nervous and afraid. The village physician, for example, suggests that the parson looks "ghost-like" as a result of wearing the veil.
The veil provokes such a strong response that much of the congregation avoids the parson. Nobody wants the honor of walking beside him, for instance, and nobody wants to converse with him.
Over time, however, the congregation changes its opinion of the veil, believing that it helps the parson to better understand their sins:

Its gloom, indeed, enabled him to sympathize with all dark affections.

The effect of the black veil, therefore, changes throughout the story, beginning with confusion and dread and later becoming a welcome sight for dying sinners.