An optics expert who earned his degrees at the forerunner of Carnegie Mellon University is one of the winners of the 2005 Nobel Prize for physics.

Dr. John L. Hall, 71, of the University of Colorado, received his undergraduate degree in 1956 and his doctoral degree in 1961 from Carnegie Institute of Technology. The professor who supervised Dr. Hall's graduate studies said that his student typically ignored his advice.

"He used his own judgment, which always turned out to be right, so I learned pretty much to let him do his thing," remembered Dr. Robert Schumacher, a Carnegie Mellon professor emeritus. "His subsequent career has been spectacular."

"It's completely amazing," Dr. Hall said of the win in an interview at www.nobelprize.org. "I hadn't, of course, expected or even contemplated [it], so it's a big surprise."

He and Dr. Theodor Hansch, 63, of the Max-Planck-Institut fur Quantenoptik in Germany, will each receive a quarter of the $1.29 million physics prize "for their contributions to the development of laser-based precision spectroscopy, including the optical frequency comb technique," said the Royal Swedish Academy of Sciences.

According to an academy press release, the physicists' work allows the color of the light of atoms and molecules to be determined with extreme precision. The technique makes it possible to make highly accurate atomic clocks and improve global positioning technology.

Dr. Roy Glauber, 80, of Harvard University, will receive the other half of the prize money "for his contribution to the quantum theory of optical coherence," the academy said. His 1963 work describes the behavior of light particles and established a foundation for the field of quantum optics.

Even as a graduate student, Dr. Hall showed great promise. He could build electronic apparatus and work very quickly, his adviser said.

Dr. Schumacher recalled suggesting that Dr. Hall use an easier, but not as good technique for a project. But when he returned from Christmas vacation, he found that his student had already finished doing it the hard way.

When it came time for the young man to leave Carnegie Tech, his professors thought about how to steer him into a career that suited his talents. They arranged a meeting for Dr. Hall with a colleague at the National Institute of Standards and Technology in Washington, D.C., and he began working with lasers, which had recently been invented.

Soon after, Dr. Hall, who is called "Jan," joined JILA, a newly founded joint institute between NIST and the University of Colorado in Boulder.

There, among other achievements, he participated in experiments in a Colorado gold mine that led to the accurate measurement of the velocity of light.

"He has been absolutely brilliant," Dr. Schumacher said.

Last year, he attended an international symposium to honor Dr. Hall when he cut back his role at JILA.

"What I didn't know until the retirement party was that he has been an absolutely super collaborator with people from all over the world," Dr. Schumacher said.

Yesterday, he sent his former student some advice along with congratulations in an e-mail.

"I told him just keep working, do it for fun," Dr. Schumacher said. "And I know he just loves to do what he does."