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Question: Do the sun's tanning rays penetrate water and to what degree?

Asked by sciencetube145 to Gioia, Iain, Jo, Leo, Mariam on 21 Jun 2010 in Categories: .

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  • Photo: Iain MoalIain Moal answered on 17 Jun 2010:

    Yes, they do penetrate water. Some of the UV is reflected from the surface (about 30% I think), so just under the surface, there is about 70% as much UV intensity. As you go deeper, the rays get scattered, just as water can scatter normal light, and it gets darker the deeper you go. As long as you can still see light underwater, you are still getting hit by UV rays. If you are waist high in water, your upper body gets even more UV than if you were just standing in the sun, because not only do you get the rays directly from the sun, but you get hit by some of the ones that get reflected too!

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  • Photo: Gioia CherubiniGioia Cherubini answered on 17 Jun 2010:

    Hi sciencetube145,

    I think I have already replied to this question!
    Speaking of personal experience, I can guarantee you that sun’s rays penetrate water and that’s why you need to have suncream on also when you are in the sea.
    However, different wavelenghts (different colours) can penetrate at different extent. For example, the blue wavelength can penetrate as far as 200 feet and this is why deep water looks like bluish,

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  • Photo: Mariam OrmeMariam Orme answered on 20 Jun 2010:

    Yes, ultraviolet (UV) irradiation (which is what makes you tan or burn) can penetrate the water. I’m not sure how far they can penetrate, but if you’re swimming outdoors you should make sure you have waterproof suncream on to stop your skin from burning.

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  • Photo: Leo GarciaLeo Garcia answered on 21 Jun 2010:

    Yes – UVA rays can penetrate into water.

    The deeper you are under water, the less UVA rays can penetrate and cause skin damage. Although this is only useful if you are scuba diving – or can hold you breath for a long time!

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