If you’ve ever wondered what ‘ultraviolet radiation’ or ‘UV light rays’ really are and why you should protect yourself from them, you’ll find some answers here in plain English.
Electromagnetic (EM) radiation is a form of energy that’s all around us, every day. It can take many forms, including radio waves, microwaves, x-rays and gamma rays. Sunlight is also a form of EM energy, but visible light is only a small portion of the EM spectrum. UV light is invisible to the human eye. It’s responsible for both sun tans and sunburn, proving that too much exposure to UV radiation can damage living tissue. As EM radiation, UV light is transmitted in waves or particles at different wavelengths and frequencies, including:
The wavelengths we can see are found in the middle of the EM spectrum, between infrared and UV. These wavelengths are approximately 380 nm to 740 nm.
As a component of sunlight, ultraviolet lies between visible light and X-rays on the EM spectrum. Its wavelengths are approximately 10 nm to 380 nm and are invisible to the human eye. Ultraviolet does have numerous medical and industrial applications but it can also damage living tissue.
Understanding the main kinds of UV light
UV light is generally divided into three bands:
UVA (wavelength 315–400 nm)
UVB (wavelength 280–315 nm)
UVC (wavelength 180–280 nm).
Only about 10 percent of sunlight is UV and only about one-third of this penetrates our atmosphere to reach the ground. Of this one-third approximately 95% is UVA and 5% is UVB (no measurable UVC from solar radiation reaches the Earth’s surface because ozone, molecular oxygen and water vapor in the upper atmosphere completely absorb the shortest UV wavelengths). Still, UVA and UVB contain the strongest electromagnetic radiation and are most damaging to living things.
Why UV can potentially cause you injury?
UV radiation has enough energy to break the chemical bonds in your body’s tissues, causing electrons to break away from various atoms in your cells. Exposure is particularly harmful for your skin and eyes, which are most adversely affected by higher-energy UVA and UVB radiation.
Artificial sources of UV radiation (like tanning booths, black lights, curing lamps, germicidal lamps, mercury vapor lamps, halogen lights, high-intensity discharge lamps, fluorescent and incandescent sources, and some types of lasers), can also be dangerous to your skin and eyes.
How UV enters your eyes
There are two types of light that enter your eye – ultraviolet (UV) and visible light. You can’t see UV light but your cornea (the front of your eye) and lens naturally absorb it to reduce the amount of UV rays that reach your retina (the back of your eye). Sunshine can penetrate your eyes at different depths. In adults only 1% of incoming UV radiation reaches the retina (back of the eye) because the cornea (or the outermost layer of the eyeball) and lens filter it out. UVA passes through straight to your lens while your cornea and lens completely absorb UVB. By contrast, visible light easily penetrates through to your retina where it activates the chain reaction of biochemical processes needed for us to see the world around us.
The Eye – a marvel of evolution.
Even though your eye occupies less than 2 percent of your body’s surface area, it’s the only organ system that allows visible light to penetrate the body. Over the course of human evolution, we’ve also developed mechanisms to protect our eyes from the harmful effects of the sun’s rays, including:
- A recessed position within the head
- Shielding by the brow ridge, eyebrows and eyelashes.
However, these adaptations can’t protect our eyes from extreme UV conditions, such as sunbeds and strong reflections from snow, water and sand. When activated by bright visible light, your eye minimises UV penetration by narrowing the pupil, closing the eyelids or the squinting reflex. But, on a cloudy day, exposure to UV radiation may still be high – your eyes may not activate their natural defence mechanisms to protect you from UV damage. That is why we always recommend wearing sunglasses, and especially a well known sporting/ outdoor brand like Mont Blanc or Oakley sunglasses. They have been shown time and again to offer the best and most consistent protection against the elements. In such circumstances:
UV-A (wavelength 315-380nm) may penetrate deeply into your skin and eyes, where it can harm your central vision. It can damage the macula, a central part of the retina at the back of your eye.
UV-B (smaller wavelength, 280-315nm) doesn’t penetrate into your skin and eyes like UV-A. The front part of your eye (the cornea and the lens) absorbs most UV-B rays, but these can still cause more damage than UV-A rays.
Important note: you shouldn’t completely avoid sun exposure. Sunlight also delivers vitamin D to our bodies, so protected exposure is critical to normal good health and vitality.