>>9760951The energy is still there.
The equations are linear, so the beams simply pass through each other and go their separate ways.
"But what if I put an object at the intersection point?"
OK, what's happening when a beam of light (an oscillating electric field) hits an atom. The atom is jerked back and forth. We call atomic vibrations "heat".
What happens when you shove an object to the left and I, simultaneously, shove it to the right with equal force? The object doesn't move. It doesn't gain KE. It's not absorbing energy. Conversely, you and I aren't losing any energy either. We may puff and pant but so long as force is applied over zero distance, we've not doing any work.
So two beams, exactly out of phase will pass THOUGH the material until they reach a point where the cancellation is no longer perfect. That's obviously inevitable if the frequencies or directions don't match.
But what if they did match? Only way that could happen is if you shot one monochromatic beam (A) right through the source of another monochromatic beam (B).
A and B could be lasers, but I'm trying to be non-specific.
If A and B are out-of-phase, then B would simply absorb energy from A and be heated, thus putting an end to A.
So you CAN'T have two beams which remain out of phase indefinitely.
