Are ultraviolet rays stronger on cloudy days than on sunny days?

The ultraviolet rays on cloudy days are not as strong as those on sunny days.

1, the ultraviolet intensity is divided into 5 levels: 1 level is the weakest, usually indicating rain; Level 2 is weak and generally cloudy; Level 3 is medium, generally cloudy, and occasionally a little sun can be seen from the clouds; Level 4 is strong, generally sunny; Level 5 is the strongest, usually showing particularly sunny weather.

2. Generally, the ultraviolet index at night is 0, and when there are no clouds on sunny days, the ultraviolet ray is strongest in tropical or plateau areas, with the index of 15. It can be seen that the greater the ultraviolet index value, the greater the harm of ultraviolet radiation to human body, and the greater the harm to skin in a short time.

Ultraviolet (UV) is the general name of radiation with the frequency of 750 THz ~ 30 PHz in the electromagnetic spectrum, which corresponds to radiation with the wavelength of 400 nm ~ 10 nm in vacuum, and it cannot cause human vision. It is invisible light with higher frequency than blue-violet light. The English name of Ultraviolet ray is ultraviolet, in which ultra- means "above, 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.