Human eye can see invisible infrared light

Science textbooks say we can’t see infrared light. Like X-rays and radio waves, infrared light waves are longer than the light waves in the visual spectrum. But an international team of researchers has found that under certain conditions, the retina can sense infrared light after all. The eye can detect light at wavelengths in the visual spectrum. Other wavelengths, such as infrared and ultraviolet, are supposed to be invisible to the human eye, but Washington University scientists have found that under certain conditions, it’s possible for us to see otherwise invisible infrared light. Researchers used cells from the retinas of mice and people, and powerful lasers that emit pulses of infrared light, the researchers found that when laser light pulses rapidly, light-sensing cells in the retina sometimes get a double hit of infrared energy. When that happens, the eye is able to detect light that falls outside the visible spectrum.