If g_e and g_m are the accelerations due to gravity on the surfaces of the earth and the moon respectively and if Millikan's oil drop experiment could be performed on the two surfaces, one will find the ratio

(electronic charge on the moon) / (electronic charge on the earth) to be :-

(A) 1

(B) 0

(C) g_e/g_m

(D) g_m/g_e

Please explain.

let the magnitude of electric field used is E...

magnitude of charge at moon and earth are q_m & q_e respectively....

at moon

              Eq_m=mg_{m ..................1}                      

 at earth

            Eq_e=mg_e ..................2

balancing the gravitational force by electric force

dividing 1 and 2

        q_m/q_e=g_m/g_e ........

option d is correct