Outdoor tanning is influenced by which factor?

Outdoor tanning is significantly influenced by the time of day because the intensity of ultraviolet (UV) radiation varies throughout the day. UV rays are generally strongest between 10 a.m. and 4 p.m., which is when sun exposure can lead to more effective tanning. During these hours, the angle of the sun is higher, allowing for more direct exposure to UV radiation, which stimulates the production of melanin in the skin—this is responsible for tanning.

Other factors such as skin type play a role in how an individual tans and their susceptibility to sunburn, but they do not directly influence the tanning process itself in the same way that the time of day does. Indoor tanning equipment is related to artificial tanning methods and is not relevant to outdoor tanning. Personal health can affect skin sensitivity and the ability to tan safely but does not influence the external environmental conditions that determine UV intensity and exposure at different times of the day.