There is no electron at all until it was recorded by the screen. The electron went through one of the slits, but it is impossible to know which one. You are asked to design a camera to record the license numbers of speeding cars from a plane. The plane is to fly 2 miles up in the air so it isn't noticed. Give just a number, and state what assumptions you need to make.
Imaginary quantities Let z be a complex number.
You may change your mind as often as you wish.