An electron is diffracted like a wave when it passes through a double slit, which is narrower than the de Broglie wave length of electron. However, doesn't electron interacts with its surrounding ? (air molecules, screen, etc.) And since interaction equals to observation, isn't the electron observed? How can an electron diffracts eventhough it is involved in various interaction? These questions probably arise due to my lack of understanding of wave-particle duality. Any advise is welcomed.