Answer:
Infrared
Step-by-step explanation:
Infrared radiation is the form of light that is invisible to eye but can be felt as warmth.
Electromagnetic radiation has gamma rays, ultraviolet rays, x- rays , visible light and infrared radiation, etc.
The heated surface usually emits infrared radiations .They form a continuous spectrum.
Infra red radiation are used in different processes such as heat sensors, thermal imaging and night vision equipment.
Broadly they can be divided into three group near, middle and long infrared radiations.
These radiations can be seen with the eyes with special equipment or under certain conditions.