2011 GS Paper I, all questions

UPSC Prelims 2011 · GS Paper I

Question 69: Science and Technology

A new optical disc format known as the Blu-ray Disc (BD) is becoming popular. In what way is it different from the traditional DVD ?

  1. 1.DVD supports Standard Definition video while BD supports High Definition video.
  2. 2.Compared to a DVD, the BD format has several times more storage capacity.
  3. 3.Thickness of BD is 2·4 mm while that of DVD is 1·2 mm.

Which of the statements given above is/are correct ?

a1 only
b1 and 2 only
c2 and 3 only
d1, 2 and 3

AnswerThe answer is (b).

Blu-ray uses a blue-violet laser with a shorter wavelength than the red laser of a DVD, so the pits can be packed much more closely: a single-layer Blu-ray disc holds 25 GB against 4.7 GB for a single-layer DVD. This is enough for high-definition video, while DVDs mainly carry standard-definition video. Both discs are 1.2 mm thick, so the claim of 2.4 mm for Blu-ray is wrong.

  • 1. DVD carries standard definition video; Blu-ray carries high definition.
  • 2. A Blu-ray disc holds several times the capacity of a DVD.
  • 3. Both discs are 1.2 mm thick.

How you could have got this

  1. If you were sure statement 2 is correct, (a) goes: it leaves 2 out.

    What you needed to know: A Blu-ray disc holds several times the capacity of a DVD.

  2. Then, if you were sure statement 3 is not correct, (c) and (d) go: each of them includes 3.

    What you needed to know: Both discs are 1.2 mm thick.

Only (b) is left. You didn’t need statement 1.

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) Misses the greater storage capacity of Blu-ray.
  • (b) Right: HD against SD, and several times more storage.
  • (c) Includes the wrong thickness claim and omits the HD point.
  • (d) Includes statement 3, but both discs are 1.2 mm thick.

Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2011, General Studies Paper I, Series A. The paper on upsc.gov.in.