What type of light causes tanning?

The correct response is based on understanding the different types of ultraviolet (UV) light and their effects on the skin. UVB light is primarily responsible for causing tanning because it stimulates the production of melanin, the pigment that gives skin its color. When skin is exposed to UVB rays, it reacts by producing more melanin to protect deeper layers from damage, leading to a tanned appearance.

While UVA light also affects the skin and can contribute to tanning, its primary role is in deeper skin penetration and can lead to aging and other skin damage rather than the initial tanning effect. UVC is largely absorbed by the Earth's atmosphere and does not reach the surface, thus it does not play a role in tanning. Visible light, while capable of affecting the skin in other ways, does not lead to tanning as a result of UV exposure.