Characteristics of Ultraviolet Light:
The sun’s light contains three types of rays, UVA, UVB, and UVC. Of these three rays, only UVA, and UVB pass through the earth’s atmospheric filter. More UVA hits the earth than UVB because the filter prevents the passage of shorter wavelengths of UVB that resemble UVC, the most dangerous of the three mentioned.
As a long ray, UVA is less wavy than UVB, which means UVA can penetrate the skin to deeper layers without causing significant damage to the top skin layers. Therefore, it can tan the skin with less risk of harming it. UVB on the other hand cannot get past the skin’s top layers. It bombards them with energy causing sunburns and long-term irreversible skin damage. That’s why UVA is often called the “GENTLE TANNING RAY” and UVB is called the “BURNING RAY”.