Sure, it reflects off the metal wall. That's why it is safe to be near a microwave oven while
it is on; the metal keeps the microwaves in.
But if the waves bounce back, don't they "interfere" with themselves?
Yup, but that's a useful thing. Take a look at the demonstration below. The two gray waves are
moving in opposite directions, as if they are just bouncing back and forth. The red wave is the
"sum" of the two gray waves as they interfere with each other.
Cool...the red wave doesn't look like it is moving anywhere, it is just moving up and down.
And if I change the wavelength of the gray waves, the red wave changes with them.
Right. We call this a "standing wave" because it doesn't seem to move. The points on the red
wave that don't even move up and down are called "nodes" and those are the cold spots in
Why is the red wave taller than the gray waves?
Remember, we're adding the waves together. In fact, we now have to look at what happens
to the red wave as the gray wave bounces back and forth not just once but many, many times...