Reflectance spectrometry uses which of the following?

• A. Luminometer
• B. Tungsten-halogen lamp
• C. Photomultiplier tube
• D. UV lamp

Answer: (B)

The key idea is having a broad, stable light source to illuminate the sample so you can measure its reflectance across a range of wavelengths. A tungsten-halogen lamp provides a smooth, continuous spectrum in the visible (and into the near-infrared) with good stability and high radiant flux, which makes it ideal for reflectance measurements where you need consistent illumination across wavelengths. A luminometer is built for detecting luminescence, not for providing illumination for reflectance. A photomultiplier tube is a detector component, not the light source. A UV lamp emits mainly ultraviolet light and isn’t as versatile for general visible-range reflectance. So the tungsten-halogen lamp is the best fit.