2 physics questions--light and transparent materials?

[lalalaa]

1. Different bells and tuning forks have their own natural vibrations, and emit their own tones when struck. How is this analogous to atoms, molecules, and light?

2. Light incident upon a pane of glass slows down in passing trhough the glass. Does it emerge at a slower speed or at its initial speed? Explain.

Please help, thanks so much!!