In a mass spectrometer, a beam of ionized isotopes is directed into a uniform magnetic field directed perpendicular to the plane of the paper.
An isotope X X\,X of mass 16.0 u16.0\text{ u}16.0 u and charge +e+e+e enters the field with kinetic energy EkE_{\text{k}}Ek and follows a circular path of radius RX=24.0 cmR_X = 24.0\text{ cm}RX=24.0 cm.
Another isotope Y Y\,Y of mass 4.0 u4.0\text{ u}4.0 u and charge +2e+2e+2e enters the same uniform magnetic field with the exact same kinetic energy EkE_{\text{k}}Ek.
What is the radius RY R_Y\,RY of the circular path followed by isotope YYY?
3.0 cm3.0\text{ cm}3.0 cm
6.0 cm6.0\text{ cm}6.0 cm
12.0 cm12.0\text{ cm}12.0 cm
24.0 cm24.0\text{ cm}24.0 cm