Vijay Pande, from Langley High School, pulled out of his wallet a piece of paper with the name "Viktor Nikitin" on it, and the address, "Soviet Embassy, 2552 Belmont Road, 20008."

"He said he was an assistant naval attache, and he wanted me to mail him a copy of my paper," said the 17-year-old Pande, who has created computer software that seems to demonstrate that the Strategic Defense Initiative is not practical at foreseeable levels of laser technology.

Pande is one of the 40 finalists nationwide in the 47th annual Westinghouse Science Talent Search. All were exhibiting their work at the National Academy of Sciences here yesterday.

Nearby, Lucy Erin O'Brien, also of Langley High School, said she had faced two hurdles to gaining recognition from her classmates when she was honored as a Westinghouse finalist.

First, the substance the 17-year-old had been studying -- paraquat -- didn't mean much to most of her contemporaries. It was only the '60s generation -- her teachers -- who instantly knew it as a herbicide with potential human health hazards which, in their youth, had been widely sprayed on marijuana.

Second, many of her classmates at Langley -- noted more for its humanities orientation than for science -- did not quite understand why the faculty was so excited that not one but two Langley students had placed in the prestigious science competition.

The unlikeliness of such lightning striking twice in one American high school set off a rump session yesterday on scientific success. The participants were three Fairfax County science teachers visiting the exhibition.

James Bryant, who teaches physical science to gifted and talented eighth graders at Longfellow Intermediary, was beaming like a proud father: He had had Pande and O'Brien in the same "truly outstanding" class of 1983-84. His wife, Jeannette Bryant, teaches gifted and talented third through sixth graders at the Forest Edge Center Elementary School in Reston. Jean McNeal teaches chemistry at Langley.

Three factors they agreed upon were:The two teen-agers possessed certain capabilities. "They're both so well organized. They put material together without much wasted time and motion," said Jeannette Bryant.

The two had parents who had been willing to put in time on their children's interests -- from driving them to laboratories when they needed to do research, to helping them find out who knew the answers to their questions.

They had become motivated at an early age.

"They discovered you can't fuzz your way through," McNeal said. "So much is touchy-feely today. When you say there are standards, kids rebel. In this society, we want everybody to succeed. That lessens the standards that allow us to move forward. That's the conflict we face as teachers."

Glenn T. Seaborg, a Nobel laureate in chemistry who is the president of Science Service, which conducts the Westinghouse search, cited two additional factors. The two had been blessed with good teachers. "Too many American children don't have teachers trained in math and science. They lack the interest to get students excited." Both teen-agers had parents who were immigrants. Said Seaborg, who was born in Michigan but whose first language was Swedish: "The first generation seems to get that motivation. They feel that they just have to work harder."