Does the strength of an electromagnet increase or decrease when you put the current in the opposite direction

The answer to that question is "No".

But its direction reverses.

in this image, you can see solar radiation going through ocean water.

no image, but probably absorption

luster is not a good characteristic to use by itself because luster is the property of minerals that indicates how much the surface of a mineral reflects light. the luster of a mineral is affected by the brilliance of the light used to observe the mineral surface.