Question: Why is ice clear and snow white?

Nathan Langford answered on 2 Jul 2012:

Hi zmzmzm,

This is to do with the structure of snow and ice. Ice is generally made up of one big crystal of solid water, whereas snow is made up of lots of tiny particles of ice of all different shapes and sizes. As a result, when you shine light on ice, you get a little bit of reflection, like on glass, but most of the light passes straight through into the ice and out through the other side. As a result, it just looks either dark (if there is no light coming from behind) or clear, like glass. But when light falls onto snow, it reflects and refracts off every new surface it comes to (off all the little particles), so the light gets bounced around and around and comes back out towards the person looking at it. Because most of the light comes back out, the snow ends up looking white (like a sheet of paper does, because most of the light bounces off the sheet of paper). Light only normally bounces around when it passes from one material (e.g., solid water) into another (e.g., air) – at surfaces – ice only has a couple of surfaces to reflect off.

Hope that helps…
Cheers,
Nathan.