Directions (1-4) : Read the following passage carefully and answer each of the questions given below it in the context of the passage.

Night vision goggles work on the principle of infrared radiation. Infrared rays are electromagnetic radiation that cannot be seen by the human eye. It radiates from any object (even a table) in relation to its temperature. A hotter body radiates more infrared radiation. A night vision goggles receives this radiation from the surroundings and makes out places which are comparatively warmer (usually warm- blooded animals like human beings) helping the user to see in the dark or through a fog.

Question-3 : Infrared radiations are-