2012 GS Paper I, all questions

UPSC Prelims 2012 · GS Paper I

Question 20: Science and Technology

Electrically charged particles from space travelling at speeds of several hundred km/sec can severely harm living beings if they reach the surface of the Earth. What prevents them from reaching the surface of the Earth?

aThe Earth's magnetic field diverts them towards its poles
bOzone layer around the Earth reflects them back to outer space
cMoisture in the upper layers of atmosphere prevents them from reaching the surface of the Earth
dNone of the statements (a), (b) and (c) given above is correct

AnswerUPSC’s answer is (a).

The Earth's magnetic field (the magnetosphere) deflects charged particles from the Sun and space, guiding them towards the poles, where they cause auroras. The ozone layer absorbs ultraviolet radiation, not charged particles, and moisture in the upper atmosphere does not stop them. Remember: magnetic field for charged particles, ozone for ultraviolet.

Why each option is right or wrong
  • (a) Correct: the magnetic field diverts charged particles towards the poles.
  • (b) Wrong: ozone absorbs ultraviolet radiation; it does not reflect charged particles.
  • (c) Wrong: atmospheric moisture does not stop charged particles from space.
  • (d) Wrong: statement (a) is correct.

Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.

Practise this paper timedPrevious questionNext question

Source: UPSC, Civil Services (Preliminary) Examination 2012, General Studies Paper I, Series A. The paper on upsc.gov.in.