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| The sun induces three types of radiation : 700 nm (red) and 400 nm (violet) rays, visible to the human eye, and infrared rays (IR) and ultraviolet rays (UV), which are invisible. Unlike IR rays, which cause a feeling of great heat and thus warn us, UV rays cause no skin pain, which is why we feel no particular need to avoid them. Now, as we know, exposure lasting too long may induce sunburn and, in the longer term, lead to the development of important skin damages. |
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