Detectors outside the visible range are infrared and ultraviolet detectors.

Detectors outside the visible range are infrared and ultraviolet detectors.

• A. Infrared and Ultraviolet Detectors
• B. Ionization Detectors
• C. Photoelectric Detectors
• D. Calorimetric Detectors

Answer: (A)

Detectors outside the visible range are designed to sense energy that the eye cannot see, specifically infrared and ultraviolet radiation. The visible spectrum runs roughly from 400 to 700 nanometers, while infrared wavelengths are longer and ultraviolet wavelengths are shorter. In fire detection, flames emit characteristic radiation in these non-visible bands, so detectors are built to respond to either ultraviolet or infrared emissions. This makes infrared detectors and ultraviolet detectors the ones that operate outside the visible spectrum. Other detector types use different sensing principles not tied to non-visible wavelengths: ionization detectors monitor current changes caused by smoke particles, photoelectric detectors rely on visible-light scattering from smoke, and calorimetric detectors measure heat. So the statement identifying infrared and ultraviolet detectors as the non-visible options is accurate.

Detectors outside the visible range are designed to sense energy that the eye cannot see, specifically infrared and ultraviolet radiation. The visible spectrum runs roughly from 400 to 700 nanometers, while infrared wavelengths are longer and ultraviolet wavelengths are shorter. In fire detection, flames emit characteristic radiation in these non-visible bands, so detectors are built to respond to either ultraviolet or infrared emissions. This makes infrared detectors and ultraviolet detectors the ones that operate outside the visible spectrum. Other detector types use different sensing principles not tied to non-visible wavelengths: ionization detectors monitor current changes caused by smoke particles, photoelectric detectors rely on visible-light scattering from smoke, and calorimetric detectors measure heat. So the statement identifying infrared and ultraviolet detectors as the non-visible options is accurate.