We know that UVB rays are the rays that cause sunburns.

我们知道中波紫外线会造成晒伤。

UVA, UVB, and UVC are classified according to their wavelengths.

a波紫外线，b波紫外线，和c波紫外线是由它们的波长来区分的。

For decades, FDA regulations required that sunscreens protect against UVB, but not necessarily against UVA.

几十年来，美国食品及药物管理局的标准是防晒霜需要防护中波紫外线，而不一定要能防护长波紫外线。

But too much UVB causes damage to your cells' DNA, leading to sunburn and ultimately skin cancers.

但是过多的 UVB 会损害细胞的 DNA，造成灼伤，并最终导致皮肤癌。

Use sunscreen that is SPF 15 or higher and says " Broad Spectrum" or " UVA-UVB protection" on the label.

使用SPF 15或度数更高的防晒霜，并在标签上标有“广谱”或“防紫外线”。

But only some protect against both UVB and UVA rays.

但其中只有几种可以同时防护中波紫外线和长波紫外线。

SPF is a nonlinear scale of how much UVB radiation is needed to give protected skin a sunburn.

SPF是一种非线性的比例，关于的是造成晒伤的b波紫外线的量。

UVB in small amounts actually helps us make vitamin D, which enables our bodies to build and maintain strong bones.

少量的b波紫外线可以帮助人体产生维他命D，它能让我们的身体保持强壮的骨骼。

SPF 15 does a pretty good job by blocking 93% of UVB rays.

SPF15的防晒可以阻挡93%的b波紫外线。

We know that UVB rays are the rays that cause sunburns.

Desai：我们知道 UVB 射线是导致晒伤的射线。

Car windows block UVB, the burn rays, but not UVA, the aging rays.

车窗可以隔绝晒伤射线UVB，却挡不住老化射线UVA。

Regular glass blocks UVB, the more energetic kind of light that mainly causes sunburns and certain kinds of skin cancer.

普通玻璃阻挡UVB，UVB是较强的光，能导致晒伤，引发特定皮肤癌。

Offers your skin broad-spectrum protection from UVA and UVB.

为您的皮肤提供广谱保护，抵御 UVA 和 UVB。

The main DNA-damaging culprit is the medium-energy UVB, which you encounter pretty much any time you go outside.

破坏 DNA 的主要罪魁祸首是中等能量的 UVB， 您每次外出时几乎都会遇到这种情况。

Bose says they are shatter- and scratch-resistant, and they have UVA and UVB protection.

Bose 表示它们具有防碎和防刮擦功能，并且具有 UVA 和 UVB 防护功能。

Short wavelength UVC never reaches the Earth's surface, but UVB and UVA do.

短波 UVC 永远不会到达地球表面，但 UVB 和 UVA 可以。

And it produced the ozone layer, which protects modern life from the harmful effects of the sun's UVB radiation.

它产生了臭氧层，保护现代生活免受太阳 UVB 辐射的有害影响。

Medium wavelength UVB rays can enter the skin's superficial layers and long length UVA rays can penetrate into the deeper layers.

中等波长的b波紫外线 可以进到皮肤的表层，而长波长的a波紫外线 则可进入皮肤的深层。

To figure out how much UVB something blocks, you'd think scientists would use some sort of skin-like compound in a Petri dish.

为了算出有多少 UVB 会被阻挡，你可能认为科学家会在培养皿中用一些类似于皮肤的化合物。

However, prolonged exposure to UVA and UVB can damage DNA, age your skin, and promote the development of potentially deadly skin cancer.

然而，过长的暴露在a波和b波紫外线下会损坏DNA，并使皮肤衰老，还会增加得致命性皮肤癌的可能。