Answer: Interference
The Principal of superposition of the wave
Let’s look at an example to understand superposition principal, When we drop a pin in a tank we see some circular waves when another pink is dropped we see some more waves. These waves are traveling in the same tank and at one point these waves superimpose on each other
Wave theory of light includes the phenomena of diffraction and interference.
We know that two or more wave motions travel at the same time in space. Sometimes these two wave motions combine and some physical effect takes place and interference is one effect .When two or more waves cross each other in the same medium they both interfere which is known as the interference of waves.