How does sunscreen work?

防晒霜是如何起作用的？

People are advised to drink plenty of fluids, wear lightweight, light-coloured clothing, and a wide-brimmed hat, and to use a high-factor sunscreen when a heatwave occurs.

在热浪来袭时，（专家）建议人们多喝水，穿轻薄、浅色的衣服，戴宽檐帽，使用防晒系数高的防晒霜。

Most of us are familiar with sun protection factor (SPF), the big number on the front of your sunscreen bottle. The higher the number is, the greater protection it offers. 

我们大多数人对防晒系数（SPF）都很熟悉，即防晒霜瓶子前面标注的一个大数字。数字越大，它提供的保护作用就越大。

SPF tells you how much protection your sunscreen provides from UVB radiation. Ultraviolet A and B refer to different wavelengths of radiation from the sun that enter the earth's atmosphere.

防晒系数（SPF）表示防晒霜对中波紫外线的防御程度。紫外线A波和B波指的是进入地球大气层的太阳辐射的不同波长。

UVA is associated with ageing of the skin and pigmentation as well as skin cancer, particularly squamous cell carcinoma (the second most common type). It can affect human skin even through glass.

长波紫外线UVA与皮肤老化、色素沉着以及皮肤癌，尤其是鳞状细胞癌（第二种最常见的皮肤癌）有关。它甚至可以穿透玻璃影响人体皮肤。

重点词汇

1. sunscreen: a substance that you put on your skin to prevent it from being damaged by the sun  防晒霜，防晒油

• Use a sunscreen suitable for your skin type.

2. fluid:  a substance that flows and is not solid  液体；流质

• If you have a fever you should drink plenty of fluids.

3. pigmentation: the natural colour of something, usually a living thing （生物的）天然颜色

• I have a skin disorder, it destroys the pigmentation in my skin.