UPSC Prelims 2009 Q68: Science & Technology – Physics

UPSC Prelims 2009, General Studies Paper I · Science & Technology

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

Answer: (c) Infra - red waves

Explanation

Which waves power night vision devices

Night vision technology detects a specific type of electromagnetic radiation invisible to the naked eye.

Option	Verdict	Reason
(a) Radio waves	Incorrect	Radio waves are not used for this imaging purpose
(b) Microwaves	Incorrect	Microwaves are also not the basis of night vision technology
(c) Infra-red waves	Correct	Night vision devices detect the infra-red radiation emitted by warm objects (heat signatures), converting it into a visible image
(d) None of the above	Incorrect	Option (c) is correct, so this is wrong

Night vision technology facts:

Point	Detail
Detects	Infra-red radiation (heat signatures)
Application	Thermal/night vision imaging

Answer: (c) Infra-red waves.

(a) Incorrect. Radio waves are unrelated to night vision imaging.
(b) Incorrect. Microwaves are also not the basis for this technology.
(c) CORRECT. Night vision devices detect infra-red radiation, converting heat signatures into visible images.
(d) Incorrect. Option (c) is the correct answer, so 'none of the above' is wrong.

Night vision apparatus detects INFRA-RED WAVES (heat signatures from warm objects), converting them into a visible image.

Night vision apparatus uses infra-red waves.

Confusing infra-red (heat-based) imaging with radio or microwave technologies.
Not understanding the basic thermal-imaging principle behind night vision devices.
Assuming all 'invisible wave' technologies work the same way.

Night vision = infra-red detection (heat signatures). A fundamental physics-application fact.