What happens when an electromagnetic wave reflects of a surface at an 90 degree angle and continues moving along the same path as it came from? Will the two waves that are moving in opposite direction interfer with each other to from a standing wave pattern? This seems to be the case when you tie one end of a string to something and then move the other end to form a wave like pattern. After having reflected the 2 waves create a standing wave. I doubt this happens with electromagnetic waves, but I have no to way to test it. Can electromagnetic waves form standing waves under any conditions? Thank you.