Question

Is light opaque?

Answer 1

An opaque object is neither transparent (allowing all light to pass through) nor translucent (allowing some light to pass through).

Although it seems to be transparent. It is actually opaque.

Ever seen a bullet proof glass panel at a bank. That is a thick panel of glass. And the color that you see through it is already not the same. If you look side ways into the edge if a pane of glass you will see it has a greenish tint to it and you can not see all the way through it.

So although it is almost transparent, it is not, so it has to be considered to be opaque.