Dual Nature of Radiation and Matter - Result Question 65
69. 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
[1994]
(a) $1 / 2$
(b) 2
(c) $1 / \sqrt{2}$
(d) $\sqrt{2}$
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Answer:
Correct Answer: 69. (d)
Solution:
- (d) $\frac{1}{2} m v^{2}=eV$, or, $v=(2 eV / m)^{1 / 2}$
The mass of helium ion is four times that of hydrogen ion. Further, the charge on helium ion is twice that of hydrogen ion.
$\therefore v _{H e} / v_H=\sqrt{2}$
