A particle of charge equal to that of an electron e , and mass 208 times the mass of electron (called $\;\mu-\;$ meson ) moves in a circular orbit around a nucleus of charge +3e . (Take the mass of nucleus to be infinite ) . Then radius of $n^{th}\;$ Bohr orbit is

Question

$(a)\;\large\frac{\varepsilon_{0} n^2 h^2}{2 \pi m_{e} e^2}\qquad(b)\;\large\frac{\varepsilon_{0} n^2 h^2}{4 \pi m_{e}e^2} \qquad(c)\;\large\frac{\varepsilon_{0} n^2 h^2}{8 \pi m_{e}e^2} \qquad(d)\;\large\frac{\varepsilon_{0} n^2 h^2}{624 \pi m_{e}e^2}$