How Christmas Lights Work

By: Marshall Brain

LED Christmas Lights and Projectors

Holiday projector, colored light
Holiday projectors are a quick and easy way to decorate the outside of your house for Christmas. Marta Iwanek / Contributor/Getty Images

Two new developments in Christmas lights are LED lights and holiday projectors.

LED Lights

Henry Joseph Round was credited with the discovery of the light-emitting diode (LED) in 1907, but it wasn't until the 1960s that LEDs were used commercially. LED lights don't have filaments that will burn out and they generate light without adding heat. LEDs are illuminated by electrons moving in a semiconductor material. The first LED Christmas lights were sold in 1998, and by the mid-2010s, Christmas trees at both the U.S. Capitol and Rockefeller Center had been lit using only LED lights [source: Gardner]. Even though they cost consumers more upfront, LED lights use 80 percent less energy and last much longer than traditional incandescent lights [source: Wood and Gerrity]. An added benefit is that these lights are often programmable, allowing users to change the color of the lights and select different blinking modes. They also come in a variety of shapes and styles.


LED Holiday Projectors

Laser projectors are no longer just for night clubs. Now your house can get in on all the kaleidoscopic fun! Holiday projectors first appeared on the U.S. market in 2015 [source: Kavilanz]. When these projectors are pointed at a house, they create special effects like falling snow or flying reindeer. Here's how they work: Light is passed through a lens, which magnifies and displays a picture. Unlike traditional projectors which use light bulbs, laser projectors use LEDs to produce the light [source Poretsky]. Holiday laser projectors are popular because they're easier to set up than string lights, especially when decorating roof tops.

However, these projectors can disrupt air traffic if they aren't used properly. As of June 30, 2017, there were 2,933 laser incidents involving aircraft reported to the FAA, less incidents than in 2016, but more than in 2015 [source: Patrick Murphy]. When lasers hit airplanes, the pilot and other crew members may experience temporary blindness, headaches and watery eyes. It's important that consumers point these projectors directly at their homes, not at the sky.

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