OT:Tempted to get this book

[Fyron]

Kamog said:
A light beam shining through glass will slow down and it does speed up again once it exits the glass. Why does it speed up again when it exits the glass? That's a good question, and I don't know why. I'm very curious as to what the reason is. But I think the reason a block of glass will heat up when light is shined though it is because the glass is imperfect and not completely transparent. Part of the light is absorbed and turned to heat. So not all the light emerges from the other side.

It doesn't actually slow down, it just refracts within the glass and appears distored...