# Quantum Mechanics - Quick integral probability question

1. Nov 18, 2013

### binbagsss

Okay so my book says (the context is electron hydrogen energy levels) the probability of finding the electron within dv=dv(r,∅,θ) is :

ψψ*r^2sinθdθd∅ [1]

where ψ is the wavefunction

And to find within dr of r is : ∫∫ψψ*r^2sinθdrdθd∅,[2] where the inner integral ranges over 0 to PI and the outter from 0 to 2PI

I don't really understand this. Why doesn't the first integral [1] for dv not require dr? As isnt the volume element given by r^2sinθdrdθd∅?

I also dont really understand why we don't need to include some integral limits corresponding to dr in [2]

If anyone can help explain things this would be greatly appreciated . Ta in advance !!

2. Nov 18, 2013

### Simon Bridge

Looks like a typo to me.