Why are ultraviolet rays stronger on cloudy days?

The intensity of ultraviolet rays on cloudy days is the same as that on sunny days. The ultraviolet rays on cloudy days are very strong, and the clouds have almost no isolation effect on UVA ultraviolet rays. All ultraviolet rays can penetrate clouds, and 90% ultraviolet rays can penetrate clouds. Only dark and big rain clouds can block some ultraviolet rays. On cloudy or rainy days, ultraviolet rays are sometimes particularly strong, because the reflection of clouds is mainly visible light, and ultraviolet rays are not reflected. When it is cloudy or cloudy, the ultraviolet rays will not weaken much.

Ultraviolet is the general name of radiation with the wavelength of 400 nm ~ 10 nm in the electromagnetic spectrum, which cannot cause human vision. It is invisible light with higher frequency than blue-violet light. In English, the prefix ultra- means "above and beyond"

180 1 year, German physicist Ritter discovered that a section outside the ultraviolet end of the solar spectrum can make a photographic negative containing silver bromide sensitive, thus discovering the existence of ultraviolet rays. Ultraviolet rays can be used for sterilization. However, too much ultraviolet light can cause skin cancer.