Can an anti-ultraviolet umbrella really prevent ultraviolet rays?

As long as it is an anti-ultraviolet umbrella, it can protect against the sun, but it can't completely protect against the sun, because after all, even sunscreen can't completely protect against the sun. It can only be said that it has a certain sunscreen effect, and the best sunscreen method is not to bask in the sun. In addition, remember to use the sun umbrella separately from the umbrella, because the sun umbrella will weaken the sun protection effect if it gets wet. If it is often used as an umbrella, then this kind of umbrella has no sunscreen effect.