Ode to a Diode

Traditional lights burn white and get their color from filters. But LEDs are created out of semiconductors; changing their composition changes their color, across the spectrum from blue to red, said Nadarajah Narendran, director of research at the Lighting Research Center in Troy, N.Y. They don't heat up. Instead, the atoms have charges that combine and release light.

In strictly technical terms, Narendran explained, "They have a better sparkle."

Yesterday, just before 6 p.m. 20,280 LEDs, each bulb about the size of a fingertip, clicked on to applause from the crowd.

"This is the first time I've seen it in person. It's an awesome experience," said Craig Durmon, who was visiting from Hot Springs, Ark. He and other spectators had heard of plans to light the tree with LEDs, and several said the lighting was as good as ever.

"It looks great," said Rod Rosenboom, visiting from Parrish, Fla. Noting the extended life of LEDs, he said, "You can pass them on to your kids."

The task of designing the tree for the past 12 years has fallen to Kathy Presciano, a lighting specialist for General Electric.

In addition to the multicolored lights in the branches, there are red LEDs in the garland, and the three-dimensional star on top glows with white LEDs.

"It has a dual purpose," Presciano said. "We want to create a beautiful icon. . . . At the same time, we need to think about how to do this smarter." She said the national tree should use about 60 percent less energy this year than in previous years, thanks to the LEDs.

"It looks traditional, but behind the scenes, it's really efficient."