• Question: Why is ice clear and snow white?

    Asked by connie97 to Anil, Blanka, Cees, Emma, Mike on 26 Jun 2012.
    • Photo: Michael Cook

      Michael Cook answered on 26 Jun 2012:

      I’ve been thinking a lot about this since you asked it, and here’s my answer – I don’t know for sure though, so someone else might be able to provide a better one!

      An ice cube (or block of ice) is a solid chunk of ice, with nothing in it except frozen water. This means that when light enters the ice cube, it travels without much interruption (though it might change speed because it’s entering a different material – remember physics and refraction/reflection stuff?).

      Snow on the ground is formed by lots and lots of tiny snowflakes laying on top of one another. If you look at a single snowflake, you’ll see it’s actually see-through: – in fact most of it isn’t even ice, it’s just air you can look right through! But when you get a lot of them on top of each other, it’s very hard for light to travel through. Instead, the light gets scattered in all different directions, constantly entering and leaving snowflakes and then entering other snowflakes. The light gets broken up, so it no longer shows what’s underneath it.

      It might be wrong or incomplete, but I think that’s the reason why! Does that sound likely to you?

    • Photo: Blanka Sengerova

      Blanka Sengerova answered on 26 Jun 2012:

      I read somewhere that this is due to the fact that ice is mainly ice but snow is made up of ice with lots of pockets of air in between the ice and air scatters light in different ways. But how exactly this happens, I’m not too sure.

    • Photo: Emma Trantham

      Emma Trantham answered on 26 Jun 2012:

      I agree with Michael and Blanka – I think it’s to with the fact that snow is lots of ice crystals on top of each other with air in between whereas a single cubic block of ice is only water and so allows the light to pass straight through.

      I also wonder if the fact that the ice crystals that make up snowflakes are so many different shapes means that light is reflected from them in lots of different directions and it is this light we see that makes snow look white.

      What does everyone else think?

Comments

  • Photo: Mike

    Mike commented on :

    I wondered about this too – apparently some ice is clearer than others, and it depends on how fast it freezes. It seems lots of things affect how clear frozen water is! Great question.