The ionisation potential of mercury is 10.39 V. How far must an electron travel in an electric field of 1.5 x 106 Vm-1 to gain sufficient energy to ionise mercury?
(a) 10.39 x 1.6 x 10-19 m
(b) 10.39/ (1.6 x 10-19) m
(c) [0.39/(1.5 x 106)] x 1.6 x 1019 m
(d) 10.39/(1.5 x 106) m
