Q.
The first orbital of H is represented by ψ=π1(a01)3/2e−π/a0, where a0 is Bohr's radius. The probability of finding the electron at a distance r from the nucleus in the region dV is
This is obtained by the solution of Schrodinger wave equation.
Probability =ψ2dV
Its orbital is spherically symmetrical. Thus,
volume, V=34πr3 ∴drdV=4πr2 ∵ Probability =ψ24πr2dr.