THE HOUSE OF BLUE LIGHT
Visible light covers a range from 380 nm to 780 nm. Ultraviolet (UV) light is just slightly higher than the shorter end of the visible spectrum, so it is is invisible to human eyes. Such invisible light is divided into three zones: UVA, UVB and UVC.
UVA is the least damaging of the UV light, ranging between 315 and 380 nm. This light is used for tanning and is screened by a good pair of sunglasses. UVB is between 280 nm and 315 nm. That 280 nm and 315 nm range can be damaging to the eye if exposed to it on a daily basis, as it causes sunburn and destroys your Vitamin A reserves. If a person spends a lot of time exposed to UVB light, the end result is thickening skin and wrinkles that resemble leather. It can potentially damage the DNA and lead to skin cancer and other diseases. Damage is cumulative, as seen in lifetime beachgoers and others who spend a lot of time outdoors and start to resemble a catcher’s mitt in their skin conditions.
The final category, UVC light, is in the range of 100 nm to 280 NM. Even brief exposure to this spectrum can permanently damage human tissue. But unless someone spends a lot of time above the earth’s ozone layer, which absorbs most of this radiation in the upper atmosphere, there are no worries.
Not all blue light is bad. It actually helps to regulate pupil size when it is around 480 nm wavelength. That so-called blue-turquoise light range, generally around 465 nm to 495 nm, also plays a role in regulating the Circadian sleeping/waking cycle, which is essential to the body's health. If a person doesn't receive enough blue-turquoise light, the sleep cycle can be thrown off, with severe consequences to the attention span and general functioning.
But because the effects of blue light are cumulative, if you spend time outdoors and use a lot of electronic devices, there are concerns.