How come the pulses in destructive interference cancel out?

Question

Physics question relating to wave interference. (Please include several links explaining your answers.)

Answer 1

Hi Tony -

I have no links, but I can certainly describe what's going on.

When two wave sources interfere, they form patterns of "standing waves" where waves from each source appear to stand still instead of propagating outward. These standing waves consist of areas of constructive interference, where the wave crests from each source reinforce each other, and destructive interference, where the wave crest from one source cancels out the trough or valley from the other. In the areas of constructive interference, the standing waves are higher than those from either source (because the wave crests are piled on top of each other). In the areas of destructive interference, the waves disappear, because the crest and the trough cancel each other out. Assuming equal fixed frequencies, these near-radial standing wave patterns will remain static, while the original waves that create the interference continue to move outward from each source.

This is why when you receive the same radio signal from two sources that are next to each other on the tuner, you will hear the volume go up (really loud) and down (to near zero) in a regular beat as the standing waves are amplified or cancelled.

Answer 2

Well, I think of what the persecuted Christians go through in other countries where there is no religious freedom. They are always aware that the wicked ruler-ship of the nation will interfere with anything God is doing in their lives. An example of destructive interference would be someone reporting to the authorities that someone is reading the Bible. In North Korea that is enough to get someone arrested even though they do that in the privacy of their own homes. In fact, the teachers try to get the children to report on their parents and the authorities try to get everyone to report on anyone who has any signs of religious interest that is not what the state believes in. This is the worst kind of destructive interference. Constructive interference would be when someone interferes with the plans of the wicked to destroy Christianity in any way, shape or form. I have been familiar with these sort of things for many years now.