An electron and proton move in circular orbits in a plane perpendicular to a uniform magnetic field B. The mass of electron and proton are 9.1 x 10 -31 kg and 1.673 x 10 ^-27 kg respectively. Find the ratio of the radius of electron to the proton.
a. When the momentum of the electron is twice of the proton.
b. When the kinetic energy of the electron is four times of the proton.