Short answer questions on Solid state physics

[closed]

1. Platinum is silver and shiny. Why?
2. Aluminum oxide can be either transparent, red or blue. How?
3. Quartz is transparent. Why?

 

[berkeman]

Welcome to the PF. You must show your own attempt at answering these homework/coursework questions before we can provide any tutorial assistance -- that's in the PF Rules link at the top of the page.

So what are your answers?