What distinguishes thermal IR cameras?

Thermal infrared (IR) cameras are distinct in that they primarily detect emitted radiation, which is primarily in the infrared spectrum. All objects with a temperature above absolute zero emit infrared radiation. This type of camera measures the amount of infrared radiation emitted by objects, translating that data into images that represent temperature differences.

This capability allows thermal IR cameras to provide visibility in darkness and through obscurants like smoke or fog, as their function is not dependent on visible light. In contrast, the other options do not accurately capture the function or characteristics of thermal IR cameras. For instance, functioning only in bright light contradicts their primary purpose, sound detection is not related to their technology, and measuring light frequencies would pertain more to visible light analysis rather than infrared detection. Understanding this principle is crucial for recognizing how thermal imaging technology can be effectively utilized in various applications, such as surveillance, search and rescue, and industrial inspections.