1996 General Studies, all questions
UPSC Prelims 1996 · General Studies
Question 127: Science and Technology
The alpha particle carries two positive charges. Its mass is very nearly equal to that of
atwo protons
ban atom of helium
csum of masses of two positrons and two neutrons
dtwo positrons as each positron carries a single positive charge
AnswerThe answer is (b).
An alpha particle is a helium nucleus: two protons and two neutrons. Electrons weigh almost nothing, so its mass is very nearly that of a helium atom. Two protons would give only about half its mass, and a positron weighs about 1/1836 of a proton, so two positrons and two neutrons would be much lighter.
Why each option is right or wrong
- (a) Two protons are about half the mass, as the two neutrons also count.
- (b) Right: its mass is very nearly that of a helium atom.
- (c) Positrons are far lighter than protons, so this sum is much less than the alpha particle.
- (d) Two positrons weigh almost nothing.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 1996, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.