I have learned about the principles of quantum mechanics from two sources. The first is a book called quantum mechanics concepts and applications. The second is prof. Allan Addams lectures in MIT. But they have different opinions about what happens to the interference pattern of electrons when we observe them. Allan Adams says when we send light to the electron it changes its momentum and this causes the interference pattern to change slightly if we use low frequency light and greatly if we use a high frequency light. But the book doesn't think so. It says that when we send light, the interference disappears completely regardless of the frequency as if the electrons behave like bullets .what do you guys think about that?