Which statement about infrared imaging best describes what it measures?

• A. It measures exact temperature values across a scene.
• B. It detects differences in thermal radiation rather than exact temperatures.
• C. It only captures visible light.
• D. It only works at night.

Answer: (B)

Infrared imaging measures radiant energy in the infrared to show how temperature varies across a scene. The key idea is that the image is built from differences in thermal radiation, so you see hotspots and cooler areas as variations rather than exact numbers at every point. This differs from a claim of exact temperature values, which isn’t guaranteed because the signal depends on emissivity, distance, and atmospheric effects. Infrared cameras can work in day or night and do not rely on visible light, though some systems can estimate temperatures if properly calibrated. The essential takeaway is that infrared imagery highlights relative thermal differences across a scene.