Night vision waves — UPSC Prelims PYQ 2009 (Infra-red Waves)
Which one of the following types of waves are used in a night vision apparatus?
- Radio waves
- Microwaves
- Infra-red waves
- None of the above
Explanation
Option (c) is correct
- Night vision devices (NVDs) work mainly on infra-red (IR) radiation. All objects emit infrared rays due to their temperature (thermal radiation). Night vision goggles detect these IR rays and convert them into visible images, allowing vision in complete darkness. Radio waves and microwaves are used in communication and radar, not in night vision devices.
Answer: (c): Infra-red waves
