How does changing the amount of copper wire affect an electromagnets strength

More wire ===> more strength

Less wire ===> less strength

BUT . . .

This is only true if the wire is wound in a spiral around the core of the electromagnet.

If most of the wire is like, say, scattered around on the grass in the yard, then its total length has no effect on the electromagnet.  Only the amount of wire that's wound in a coil around the core of the electromagnet affects its strength.

frequency or wavelenth of em radiation in a vacuum

conduction, convection, radiation