Is the ultraviolet ray strong on cloudy days or sunny days?

Ultraviolet is the general name of radiation with the wavelength of 10 ~ 400 nm in the electromagnetic spectrum, which cannot cause human vision. 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, but too much ultraviolet rays can cause skin cancer.

Ultraviolet rays are stronger in sunny days, generally divided into five grades, and the specific analysis is as follows:

The index value is 0 to 2, usually cloudy or rainy, when the ultraviolet intensity is the weakest, and the forecast level is 1 level;

The index value is 3 to 4, generally cloudy. At this time, the ultraviolet intensity is weak, and the forecast level is level 2;

The index value is 5 to 6, which is generally cloudy. At this time, the ultraviolet intensity is strong, and the forecast level is level 3;

The index value is 7 to 9, and it is generally cloudless on sunny days. At this time, the ultraviolet intensity is very strong, and the forecast level is 4;

The index value reaches or exceeds 10, and it is mostly sunny in summer, with particularly strong ultraviolet intensity, and the forecast level is five.