Doubly ionised helium atoms and hydrogen ions are accelerated

Doubly ionised helium atoms and hydrogen ions are accelerated from rest through the same potential drop. The ratio of the final velocities of the helium and the hydrogen ion is

=	1	mv² = eV
	2

or , v = (2eV/m)^1/2
the mass of helium ion is four times that of hydrogen ion. Further, the charge on helium ion is twice that of hydrogen ion

∴	v_He	= √2
	v_H