Human eye capable of detecting smallest units of light, photons

Human eye capable of detecting smallest units of light, photons

You may not believe it, but human eyes have high sensitivity and can even detect photons. It means that human eye can see individual particles, a thing that even high-tech machines face trouble in detecting.

A new research has found that human eye is able to detect the smallest unit of light known as photons. Study’s lead researcher Alipasha Vaziri from Rockefeller University said that the eyes can detect photons under super-dark conditions. The cells in our eyes that can detect light are known as rod cells, which become sensitive in the dark.

There are around 120 million rod cells in human eyes, which as per the researchers imparts high sensitivity to human eyes. In the 1940s, it has been shown in experiments that when human subjects whose eyes had become used to the dark were able to detect flashes of five to seven photons at a time.

In the current study, the research team from Rockefeller University along with the University of Vienna in Austria carried out an experiment. For the experiment, they enrolled three men in their 20s. They were made to sit together through over 30,000 rounds of photon-delivering device. One of the participants was wearing contact lenses.

In every trial, the participants sat in a dark, sound and light-insulated room and wore headphones. They were asked to fix their right eye on a dull, red light. The participants were shown two light stimuli from the machine.

One of them was where a single photon was fired into part of retina with rod cells and another where the device was completely dark. The participants had to answer which of the two delivered the photon. Like this, the participants took more than 30,000 tests and were able to correctly detect the photon 51.6% of the time. Men were having more chances to detect a photon if a second photon was flashed a few seconds later.