hard to find ultraviolet

It turns out that the answer to this question depends on how old you are and whether you have UV-filtering lenses in your eyes.

It is important to first understand how vision works. At the back of the eye, in the retina, there are photoreceptors that detect light and send signals about the wavelengths they perceive to the brain via the optic nerve, which interprets them as color.

In fact, our blue cones can also detect some UV light. But the lens, the clear, curved structure in the eye that focuses light onto the retina to help us see more clearly, filters it out so high-energy waves never reach the cones.

This works for most people to protect the eyes from UV damage, which can age eye structures and increase the risk of cancer. But scientists say this: teenagers can still absorb a certain amount of UV light.

In a small study published in 2018 in the journal PLOS One, all University of Georgia undergraduate students were able to see UV light with a wavelength of about 315 nanometers (the full range of UV light is about 10 to 380 nanometers, with purple starting at the last mark). . The scientists concluded that during the experiment, “subjects consistently reported that the light appeared to them to be saturated violet-blue.” However, this ability disappears around the age of 30. aging ultraviolet waves reduce eyesight.

Light spectra / Photo h2odistributors / Ukrainian text 24 Channels

But some people can see much further into the UV light spectrum. Until the 1980s, cataract surgery involved removing the cloudy lens from the eye rather than inserting a new one, so people undergoing the surgery could see ultraviolet light. For these individuals and those born without lenses, UV light appears pale blue or pale purple.

Animals see more

The situation is completely different in the animal kingdom. According to a 2014 study published in the journal Proceedings of the Royal Society B, many mammals, including dogs, cats, ferrets and reindeer, They can see some wavelengths in the UV range during their lifetime. The study also notes that the ability to see ultraviolet light is common among invertebrates, fish, birds, reptiles and amphibians, which often have cones specifically designed to detect ultraviolet light and lenses that allow it to pass through.

Why do so many animals see in the ultraviolet range?

The utility for any color vision is to be able to increase contrast to detect objects or important things in your environment.
– explains biologist Michael Bock, who studies vision at Lund University in Sweden.

There are several ways that UV light helps animals do this. For example, many marine predators use ultraviolet light to see the silhouettes of their prey, such as plankton and fish larvae, because shallow waters are rich in ultraviolet light. Many insects use this type of vision to detect patterns on flowers, and some use polarized ultraviolet light in the sky to better navigate in space. Birds signal each other with their feathers using colors in the ultraviolet range and use this to locate ripe fruit.

Scientists have known since 2003 that a distant ancestor of vertebrates could see ultraviolet light and had a photoreceptor specifically designed for it. But somewhere in human evolutionary history, this photoreceptor switched to detecting violet waves rather than ultraviolet waves. Maybe because we lived longer than other animals, we couldn’t afford to damage our eyes, or maybe because the ability to see ultraviolet light turned into blurry vision for those older creatures.