In what experiments is the phenomenon of interference of electromagnetic waves observed?

To observe the interference of electromagnetic waves, you can install the transmitter horn in the horizontal plane and put the receiver opposite it at a distance of 1.5-2 m. A metal screen with two vertical slots should be placed approximately in the middle between them. Experience shows that in this case the receiver registers the maximum radiation intensity in the direction perpendicular to the surface of the metal screen passing in the middle between the slots. When the wave receiver is shifted to the right or left of this perpendicular, the intensity first decreases, then increases, then decreases again, and so on several times.