Which instrument component separates and transmits a narrow portion of the optical signal chosen from a wider range of wavelengths available at the input?

• A. Light
• B. Nebulizer
• C. Flame
• D. Monochromator

Answer: (D)

Selecting a narrow band of wavelengths from a broader spectrum is what a monochromator does. It uses a dispersive element, like a prism or diffraction grating, to separate light by wavelength and an adjustable exit slit to pass only a specific, narrow range to the detector. This precise filtering is essential for measuring or analyzing a particular wavelength without interference from neighboring wavelengths. The other items serve different roles: light is the signal itself, a nebulizer turns liquid samples into an aerosol for introduction, and a flame provides excitation energy in some analyses—none of which filter or isolate a specific wavelength.