Final answer:
A thermal imager screen may white out when it detects high levels of heat due to the overwhelming amount of infrared radiation emitted by very hot surfaces.
Step-by-step explanation:
A thermal imager screen may white out when it detects high levels of heat. Thermal imagers work by detecting infrared radiation which is emitted from objects as heat. As temperatures increase, so does the amount of infrared radiation, due to the T4 dependence (proportional to the fourth power of the absolute temperature). This means that surfaces with very high temperatures can emit such intense infrared radiation that it overwhelms the sensor, causing the screen to 'white out'. Such high infrared emissivity is also why humans are easily detected by thermal imagers, as we are nearly jet black in the infrared spectrum and our skin absorbs infrared radiation very efficiently.
In contrast, exposure to materials like water or glass does not typically cause a thermal imaging camera to white out, as these materials have different interactions with infrared radiation. Also, if a surface is at a low temperature, it would emit less infrared radiation, and therefore wouldn't be likely to cause a white out. In practical applications, thermal imagers are used for various purposes such as spotting heat leaks, optimizing industrial processes, medical imaging, and in military or law enforcement for surveillance.