Complementary properties are those properties that exclude one another, i.e., the more you know about one, the less you know about the other. For example, the wave nature and particle nature of the electron are complementary.
Work Step by Step
Which of the two complementary properties you observe depends on on the experiment you perform. In electron diffraction, when you try to observe which hole the electron goes through, you lose the interference pattern. When you try to observe the interference pattern, you cannot determine which hole the electron goes through.