# Born rule derivation?

1. Feb 12, 2013

### 71GA

Hello,

I hear a lot about the Born rule $P = |\psi|^2$ where $P$ is a probability of a particle appearing at some location and $\psi$ is a wave function.

When i look at double slit experiment interference pattern it seems to me that the pattern by itself already represents the probability that electron will hit a screen at some location. So if that interference pattern is a superposition of two wave functions i would intuitively say that:

$\begin{split} P &= \psi \\ P &= \psi_1 + \psi_2 \end{split}$

So to me it is verry bizare that in a Born rule we take absolute value of $\psi$ (why do we do that?) and square it (why do we do it?).

Is there any derivation at all on how they derived or made up the Born rule? Most of posters on other forums allways say it was a lucky guess... I can't bare the mind of that.

2. Feb 12, 2013

### Staff: Mentor

3. Feb 12, 2013

Thank you.