Is the ultraviolet ray strong on cloudy days or 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.

Extended data:

1. Ultraviolet light refers to the light with the wavelength of 100 to 400 nanometers (nm) in sunlight, which can be divided into UVA (ultraviolet A, with the wavelength of 320-400 nanometers, long wave), UVB (with the wavelength of 280-320 nanometers, medium wave) and UVC (with the wavelength of/kloc-0).

2. The electrons in the outer layer of the atom are excited to generate ultraviolet rays. The main ultraviolet light source in nature is the sun. When sunlight passes through the atmosphere, ultraviolet rays with wavelength less than 290nm are absorbed by ozone in the atmosphere.

3. Black spots caused by ultraviolet rays: ultraviolet rays with a wavelength of 320-400 nanometers are also called long-wave ultraviolet rays. The biological effect of ultraviolet rays in this band is weak, but after irradiation, the skin turns black and has obvious pigmentation, which is the black spot effect of ultraviolet rays.

4. When ultraviolet rays are irradiated, the degree of eye injury is directly proportional to time, inversely proportional to the square of the distance from the irradiation source, and related to the projection angle of light.

References:

Baidu Encyclopedia _ Ultraviolet