Why snow looks white, though ice is clear
A snowflake is made of ice, but a field of snow does not behave like a single block of ice. Sunlight entering clear ice can travel through it; in snow, light meets countless crystal faces and tiny air gaps. Each boundary redirects some of the light, sending it onward in a new direction.
A crowd of surfaces scatters the light
Snowflakes have intricate shapes, but their important optical feature is simpler: they present many ice–air boundaries. Light can bend or reflect when it crosses from one material into the other. After bouncing and changing direction repeatedly, it emerges from the snow rather than passing straight through.
Sunlight contains a range of visible colors. Snow scatters those colors broadly instead of strongly favoring one, so the colors reach the eye together and are perceived as white. The snow is not coated in white pigment; its appearance comes from what happens to light among the crystals.
Why a thick snowbank hides what lies beneath
A thin layer of snow may let some light reach the ground and return, but deeper snow gives light more chances to scatter. Eventually, very little travels straight through, and the surface appears bright and opaque. The same principle explains why a mound of crushed ice looks white while a clear ice cube can reveal the objects behind it: breaking the ice into many pieces creates far more surfaces for light to encounter.
So a snowbank is not one enormous white crystal. It is a loose crowd of small crystals and air pockets, turning incoming sunlight in many directions until the mixture looks white.
