What is the key difference between UVA and UVB rays?

The primary distinction between UVA and UVB rays lies in their effects on the skin, particularly regarding tanning and the risk of overexposure. UVA rays penetrate the skin more deeply and are primarily responsible for tanning. They can lead to skin aging and contribute to the formation of skin cancer over time due to deeper skin penetration. On the other hand, UVB rays are more intense and are primarily responsible for sunburns and the body's natural tanning response. However, overexposure to UVB rays can lead to direct DNA damage, significantly increasing the risk of skin cancer. This makes the differentiation crucial for understanding how to protect the skin effectively from sun damage.

In essence, while UVA significantly contributes to tanning by affecting deeper layers of the skin, UVB rays are associated with the risk of overexposure through more intense and direct effects, which include sunburn.