Which of the following is a characteristic of thermography?

• A. Requires visible illumination
• B. No light required
• C. Requires contact with the object
• D. Limited to a single wavelength

Answer: (B)

Thermography works by measuring the infrared heat that objects emit due to their temperature. Because this energy is emitted by the object itself, infrared cameras can create images without any visible light—so it can be used in darkness or dim conditions. This is a non-contact technique, since you observe temperature patterns from a distance without touching the object. It is not limited to a single wavelength; infrared detectors capture a range of wavelengths in the infrared band, and some systems use filters to select parts of that spectrum. It also doesn’t require physical contact with the object. Therefore, the characteristic is that no light is required.