# B Very basic probability doubt

1. Jul 6, 2016

### Naman Jain Kota

I have started quantum mechanics on my own using online lectures. So i have very basic doubts:

1) probability of electron is defined in space rather than a point. My question is why dont we comment about probability at a point.
I thought two possible explanation that:
1.1)ψ2dx the dx term goes zero so probablity at point is zero
1.2)electron is itself not a point object(which i dont know is true or not)

2)if we are given real valued wavefunction graphs can we can we comment on probablity density without knowing the complex part.(i hope not)

2. Jul 6, 2016

### BvU

Hello Naman,

1) probability density is defined. As you indicate, probability itself can only be given for a volume, not for a point.

2) no we can not. But 'real valued wavefunction graphs' are rare: most of the time we get presented amplitude graphs.

3. Jul 6, 2016

### Naman Jain Kota

Ok, so can we say probablity at a point is zero always.
And is electron point object??

4. Jul 6, 2016

### BvU

For all we know it is, yes. Limits are of the order of $10^{-20}$ m. Just try to imagine the charge density !

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