UPSC Prelims 2010 · General Studies

Question 34: Science and Technology

India-based Neutrino Observatory is included by the Planning Commission as a mega science project under the 11th Five-Year Plan. In this context, consider the following statements :

1.Neutrinos are chargeless elementary particles that travel close to the speed of light.
2.Neutrinos are created in nuclear reactions of beta decay.
3.Neutrinos have a negligible, but nonzero mass.
4.Trillions of Neutrinos pass through human body every second.

Which of the statements given above are correct ?

a1 and 3 only

b1, 2 and 3 only

c2, 3 and 4

d1, 2, 3 and 4

AnswerThe answer is (d).

Neutrinos are electrically neutral elementary particles that interact only through the weak force and gravity, so they pass through matter almost freely. They are produced in nuclear reactions such as beta decay and in the Sun; they move at nearly the speed of light; they have a tiny but non-zero mass, shown by neutrino oscillation; and trillions of solar neutrinos pass through your body every second. All four statements are correct. Remember: the India-based Neutrino Observatory is an underground project.

1. Neutrinos are chargeless and travel at close to the speed of light.
2. Beta decay emits neutrinos (strictly, antineutrinos).
3. Oscillation shows they have a very small non-zero mass.
4. Trillions of solar neutrinos pass through a person every second.

How you could have got this

If you were sure statement 1 is correct, (c) goes: it leaves 1 out.
What you needed to know: Neutrinos are chargeless and travel at close to the speed of light.
Then, if you were sure statement 4 is correct, (a) and (b) go: each of them leaves 4 out.
What you needed to know: Trillions of solar neutrinos pass through a person every second.

Only (d) is left. You didn’t need statements 2 or 3.

This follows an unofficial answer: UPSC has not published its key for this year, and if that answer is wrong, so is this path.

Which options go is worked out from UPSC’s key and the options, not by a model.

Why each option is right or wrong

(a) Leaves out statements 2 and 4, which are also correct.
(b) Leaves out statement 4: trillions pass through the body each second.
(c) Leaves out statement 1, which is correct.
(d) Right: all four are correct.

Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2010, General Studies, Series A. The paper on upsc.gov.in.