Anything above absolute zero will radiate energy. The lower the temperature, the longer the wavelength. Generally at room temperature it is infrared. When the temperature is around 800 degrees, the radiation is visible light, which is why iron burns red and you see bright light. Infrared we can not see, at night, there is no visible light, but still radiates infrared light, the temperature around people and trees, radiation wavelengths are different. Infrared night vision converts infrared light, which we cannot see with the naked eye, into visible light. Because the infrared radiation is weak, so is the visible light. The image is green, because our eyes are most sensitive to green light and easily fatigued, which helps us see the weak light better. And the difference between red and green light is only the wavelength, so’ s easy to switch. Night image is blurred Photocathode (converts photons into electrons) Microchannel plate (increases the number of electrons by high voltage) Fluorescent screen (electrons hit the screen with phosphorescent coating), so infrared night vision is mostly green
