UVA and UVB rays both contribute to skin damage from the sun. UVA tends to damage more and to penetrate deeper.
Compared to UVB rays, UVA rays enter the skin at a deeper level. These rays are to blame for the skin's aging, tanning, and wrinkle-causing effects. Wearing sunglasses that block UVA rays is a good way to stop these rays from penetrating deeply into the skin. It is advised to wear sunglasses with complete UVA ray protection. If you want to keep your arms covered, you can also put on hats and long sleeve shirts.
One of the rays that can burn the skin is UVB radiation. Apply enough sunscreen to completely cover your body. Additionally, after swimming or sweating, reapply sunscreen (every hour recommended).
A good way to prevent UVA rays from penetrating deep into the skin is to wear sunglasses that filter out UVA rays.