English: Potential V(r) of strong interaction as a function of distance r between two quarks, which can be approximated by

${\displaystyle V(r)=-{\frac {4}{3}}{\frac {\alpha (r)\hbar c}{r}}+kr}$. The vertical lines indicate rms radii of different quark-antiquark wave functions.

Reference: Gottfried Weisskopf - Concepts of Particle Physics, Vol. 1, Oxford University Press, 1984, ISBN 9780195043730