Any science textbook on vision tell us we can not see infrared light. As X-rays or radio waves, infrared waves are outside the spectrum visible to the human eye. However, researchers have found that under certain conditions the retina itself may after all perceive infrared light.
Typically a particle of light, a photon is absorbed by the retina, which then uses a molecule called photopigment, which starts the process of converting light to vision. In the standard view, each of the large number of molecules of a single photon absorbed photopigment.
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It all started when some scientists who later would integrate the research team realized that since I worked with some infrared laser, sometimes saw green flashes said laser being activated. Unlike laser pointers used in conference rooms and the like, the powerful infrared laser that emits those scientists working light waves to which it was believed entirely invisible to the human eye.
After confirming that there was no source capable of generating flashes of green light in times in which perceived in the room, came to the conclusion that, incredible as it seems, the only source of light could only be the infrared laser . But how could this be possible?
The international team of Vladimir and Frans J. Kefalov Vinberg, both of the Department of Ophthalmology and Visual Sciences at Washington University in St. Louis Missouri, United States, reviewed the scientific literature and reviewed cases of people who thought they had seen infrared light. They repeated earlier experiments that had supposedly seen infrared light, and analyzed several lasers, to see what they could find out about how and why the infrared light could turn out to be visible to the human eye.
They experimented with laser pulses of different durations that delivered the same total number of photons, and found that the shorter the pulse, the more likely that a person could see it. Although the length of time between pulses was so short that could not be appreciated by the naked eye, the existence of such pulses was very important in allowing people to see this invisible light.
Typically a particle of light, a photon is absorbed by the retina, which then uses a molecule called photopigment, which starts the process of converting light to vision. In the standard view, each of the large number of molecules of a single photon absorbed photopigment.
But packaging many photons in a short pulse of a laser with a high velocity enables two photons are absorbed simultaneously by a single molecule photopigment, and the combination of the two particles of light energy is sufficient to activate the pigment and allow the eye to see what is usually invisible.
The visible spectrum includes light waves ranging from 400 to 720 nanometers long. But if a molecule of pigment in the retina is hit in rapid succession by a pair of photons whose wavelength is 1000 nm, these light particles provide the same amount of energy that the blow of a single photon with wavelength 500 nanometers, which is within the visible spectrum. Here’s how the human eye is capable of seeing that infrared light.
This archive content was originally published December 7, 2014 (www.betawired.com)