Let \( \alpha \) and \( \beta \) be the roots of equation \( px^{2}+qx+r=0,p\neq 0 \). If \( p,q,r \) are in A.P. and \( \dfrac{1}{\alpha }+\dfrac{1}{\beta }=4 \), then the value of \( |\alpha -\beta | \) is
1
\( \dfrac{\sqrt{61}}{9} \)
2
\( \dfrac{2\sqrt{17}}{9} \)
3
\( \dfrac{\sqrt{34}}{9} \)
4
\( \dfrac{2\sqrt{13}}{9} \)