2009 General Studies, all questions

UPSC Prelims 2009 · General Studies

Question 68: Science and Technology

Which one of the following types of waves are used in a night vision apparatus ?

aRadio waves
bMicrowaves
cInfra-red waves
dNone of the above

AnswerThe answer is (c).

Night vision devices use infra-red radiation. All warm bodies give off infra-red waves, which special sensors turn into a visible image, so objects can be seen in the dark; some devices instead amplify faint light or use an infra-red source. Radio waves and microwaves are used for communication and radar, not for seeing in the dark.

Why each option is right or wrong
  • (a) Radio waves are used for broadcasting and communication.
  • (b) Microwaves are used in radar, ovens and communication.
  • (c) Right: infra-red waves are used.
  • (d) Wrong: infra-red waves are used, so one of the listed options is right.

Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2009, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.