1. Before means earlier than.
We must leave before four o'clock.
2. Before can mean in a more important position than.
She is so ambitious that she puts her job before her family.
3. Before can mean facing.
The handsome singer had many adoring fans before him.
4. Before can mean in the future.
The bride smiled as she thought of the happiness before her.
5. Before can mean in the presence of.
I was told to appear before the judge.
: Opaque Objects.
Most objects are visible to us because of the light diffusely reflected from them. A white object, such as a sheet of paper, a whitewashed fence, or a table cloth, absorbs little of the light which falls upon it, but reflects nearly all, thus producing the sensation of white. A red carpet absorbs the light rays incident upon it except the red rays, and these it reflects to the eye.
Any substance or object which reflects none of the rays which fall upon it, but absorbs all, appears black; no rays reach the eye, and there is an absence of any color sensation. Coal and tar and soot are good illustrations of objects which absorb all the light which falls upon them.