In the harsh electric light of the Washington Cathedral's War Memorial Chapel, the minister was praying yesterday for the poor and powerless, for children and peace, and for the release of the 50 American hostages in Iran.

His voice floated across the chapel expanding until it became soft and distant in the stone gray gloom high above.

Exactly a year ago, on a cloudless and chilly day so unlike yesterday's damp, the news came that a mob of Iranians had stormed the U.S. embassy in Tehran and taken hostages. Most Americans, though indignant, hoped nevertheless that the hostages would be held only a short time. But the days grew to weeks and the weeks to months, and prayer services and vigils became a way of life for the families of the hostages and others.

Yet, if yesterday was dreary, one well-choreographed for such an anniversary, there were two people sitting in the chapel who found that they could smile at last.

Frederick and Margaret Babcock sat last among pews filled with 48 vacationing parochial schoolers from Connecticut and the noon-time service regulars. Their son-in-law, Bruce Laingen, was the highest ranking American diplomat seized in Iran.

"The end is starting," the 82-year-old Babcock said with a smile, "and that's a relief."

Behind that smile was the knowledge that in the last week the Iranian Parliament had finally agreed upon a list of demands and that the president had said that negotiations could now begin in earnest.

A year ago, Margaret Babcock, 79, was at their Chevy Chase home when the phone rang. It was early, perhaps 4 a.m., and the caller was her daughter, Penne Laingen. Laingen told her mother that she had been called by the State Department with the news of the embassy seizure.

It would never last very long, Mrs. Babcock remembers thinking.

In the soaring arches above her where the charcoal shadows hung, the stained glass filtered the somber afternoon light. Blues tinted with the faintest blush of rose suffused about the stonework.

Now, she believed, she could finally say, "It gives me a lot of hope."

"I just came to ask the Lord to continue to look after our people."

Later in the afternoon, a somber Secretary of State Edmund Muskie and his wife Jane led a contingent of State Department officials attending a prayer service for the hostages at the Washington Cathedral.

But Muskie's sober face belied the joy expressed by the 20 hostages families at what they believed is the rapidly approaching end to their trial. While they waited for Muskie to arrive, the family members hugged each other and smiled.

Sadness, reflection, and occasional anger flickered on the faces of the Washingtonians yesterday who were stopped on rainy downtown streets and asked how they felt about the anniversary.

"You know, I've been thinking," said Freeman Glover, 52, a kitchen helper at the Sheraton Carlton Hotel. "Strong as this country was, it shouldn't have taken a year. If the president had pushed a little harder, we might have had to go to war. I don't like to go to war, but a large country like this, it shouldn't be shown so weak."

"I didn't believe it'd ever be a year, or even months, or even weeks," said James Farrell, recalling his reactions to the hostage-taking. A food broker who lives in Chevy Chase, Farrell said he thought the anniversary had cast a pall over election day. "Since people found out they weren't going to be released, it didn't help Carter. It may have hurt him," he said.

"I hope they set them free this time," said Tom Watkins, a clerk at Garfinckel's Tobacconists. He added that he was much more confident now that control of the hostages had been relinquished by the militant students. "There's much more hope now, at least among the [American] people," he said.

Others were not so sanguine. "I tell you the truth -- it's the same. It's going to be the same till they be released," said a woman in a nurse's uniform who declined to give her name but said she worked nights at the Veterans Administration. "I don't know when they're going to get out. I don't know what that [Iranian] government is up to. They may just be doing all this stuff to get what they want. I don't think they're going to release those hostages."

"I think about the hostages every day," said Alice Fulton, 61, as she waited for her bus late yesterday afternoon. Fulton, a 30-year employe with the Veterans Administration, was critical of President Carter. "It hurts thinking about all the political power we have and no one's made a firm decision within a year."