Which instrument determines the intensity of photons of the analytical line exiting the monochromator?

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

Answer: (B)

The detector is the instrument that determines the intensity of photons exiting the monochromator. After the monochromator selects a specific wavelength, the light still arrives as photons with a certain flux. The detector converts these photons into an electrical signal (such as a current or voltage) that is proportional to how many photons are arriving per unit time. That signal represents the intensity of the analytical line at that wavelength.

The monochromator itself only separates wavelengths and controls how much light passes through (influenced by slit width and grating efficiency), but it does not quantify the photon flux. Light refers to the radiation itself, not a measuring device. A flame can be a light source in emission methods, but it does not measure intensity. So the detector is the component that actually determines the intensity.