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The common recommendation when looking for sunglasses is to find a pair that blocks 100% of UVA/UVB radiation or offers 100% UV 400 protection. The advice is simple enough. However, this then begs the question, what is the difference between the two? Is one better than the other?
The sun emits 3 types of UV waves - UVA, UVB and UVC. Both UVA and UVB make it through to the earths surface. UVC (the most dangerous) on the other hand is mostly absorbed by the earth's atmosphere.
95% of UV radiation that makes it to the earth is UVA (this is also what is used in tanning beds). The other 5% is UVB (which is what causes most sunburns). Both types of radiation have been found to cause damage if directly exposed to our eyes.
This is the reason most experts will tell you to look for sunglasses that block 100% of UVA and UVB rays.
Simply put, UV 400 means that the lenses will block Ultraviolet (UV) waves shorter than or equal to 400 nano-meters (nm). All UV waves come in different lengths as shown in the chart below.
UVA: 320-400 (nm)
UVB: 290-320 (nm)
UVC: 200-290 (nm)
Since all of these UV rays are shorter than or equal to 400 nm, they are blocked by the lenses - keeping your eyes safely protected.
This also explains why you can still see color. The color red has a wavelength of 680 nm. Since it is greater than 400 nm, it is not blocked by the UV 400 lenses.
No, both are blocking 100% of the sun's harmful UVA and UVB radiation. As long as your sunglasses offer this protection (like all sunglasses here at STNGR), you can rest easy and always perform your best!
