科学美国人60秒:Most Laser Pointers Are Too Strong

Laser pointers are helpful when giving a presentation. Just don’t let the beam hit you in the eye—especially when it’s green. The National Institute of Standards and Technology says that nearly 90 percent of commercially available green pointers and about half of red pointers they tested are too strong and violate federal safety regulations.

Green lasers use a shorter wavelength of light than red ones, making them brighter and more dangerous. The darker part of the retina heats up from the green laser’s intense, yet invisible, infrared light, which can cause retinal scarring and even blind spots. Because the damaging wavelengths are invisible, the eye’s natural defense mechanism—its eyelid—doesn’t close to provide protection.

Airline pilots are well aware of these dangers: in 2011 alone there were more than 3,500 cases of lasers being pointed at aircraft. In July 2012 one unfortunate JetBlue pilot suffered an eye injury when someone on the ground shined a green laser through his cockpit window. Luckily, the flight landed safely. Unluckily, it didn’t land on the person pointing the laser.

—Larry Greenemeier