2000 General Studies, all questions
UPSC Prelims 2000 · General Studies
Question 101: Science and Technology
For reproducing sound, a CD (Compact Disc) audio player uses a
aquartz crystal
btitanium needle
claser beam
dbarium titanate ceramic
AnswerThe answer is (c).
A compact disc stores sound as a spiral track of tiny pits. In a CD player a laser beam is focused on the track and the reflected light changes as it passes over pits and flat areas. A detector turns these changes into electrical signals, which are decoded into sound. No needle touches the disc.
Why each option is right or wrong
- (a) A quartz crystal keeps time in watches and clocks; it does not read a CD.
- (b) A needle in contact with the groove is used in gramophone records, not CDs.
- (c) Right: a laser beam reads the pits on the disc.
- (d) Barium titanate is a piezoelectric ceramic used in some pick-ups and transducers, not for reading a CD.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2000, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.