White v Silver

[Buenchico]

Many years ago, when I was a student teacher, I had just finished a lesson about light when a 12-year-old girl asked this: "Sir, if a surface which which reflects all frequencies of light appears white, why is a mirror silver?"

30 years on, I'm still not sure exactly how I should have answered this! Any suggestions please?! (Remember that any answers should be concise and comprehensible to a 12-year-old of average intelligence!). BTW: I think that this was when I decided to teach Maths instead of Physics!

[rowanwitch]

You might like to think of it as a biology question instead. It's how our brains interpret the image rather then what is there. The way light hits the matte paper and scatters is too hard for our brain to split up so it blurs them together. Metals bounce back light that's been filtered by layers of electrons like a net over the surface so only some of it comes back. Shades of grey in the case of silver.

Or from another point of view... white paper is white unless you put a gloss coating on it then it starts to be slightly more colour reflective due to the thin layer of gloss working like thousands of little prisms breaking some of the light into colours we can see.
but you can paint something you can tell is silver using greys, and the nearby colours it reflects.

[ToraToraTora]

well the question is flawed, a white surface does not reflect all frequencies of light for a start.