Is the ultraviolet ray stronger on cloudy days than on sunny days? Why?

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, which means that 90% ultraviolet rays can penetrate clouds, and only dark and big rain clouds can block some ultraviolet rays.

On cloudy days or rainy days, ultraviolet rays are sometimes particularly strong, because clouds mainly reflect visible light and ultraviolet rays are not reflected, so the ultraviolet rays on cloudy days or cloudy days will not be weakened much.

Extended data

Hazards of ultraviolet rays:

1, blackening

When melanocytes feel ultraviolet rays, it will accelerate the secretion of melanin, and then input it into epidermal cells, and melanocytes themselves will become larger, so that the skin will turn black. Some people will get a tan immediately, while others will delay it. The role of melanin is to absorb and shield ultraviolet rays, so blackening is essentially a self-protection mechanism of the skin.

2, skin aging

Ultraviolet rays cause the decomposition and denaturation of collagen and elastin. When the skin is young, the collagen fibers are thick and clear, but when it is old, it becomes a mess, with decreased elasticity, water loss, more serious free radical damage, and rough and dull. Because ultraviolet rays are one of the factors that cause skin aging, exogenous skin aging is also called "photoaging".

3. erythema appears

Erythema is an acute phototoxic reaction, often accompanied by molting and burning pain, and can also lead to pigmentation. Ultraviolet rays can aggravate inflammation, so people with acne, damaged skin and acne marks will slowly recover after sun exposure.

Baidu encyclopedia-ultraviolet