Which component converts photons into an electrical signal for measurement?

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

Answer: (B)

Photons that reach the sensor carry information about light intensity, and the detector is the device that turns that light into an electrical signal. When illuminated, a detector such as a photodiode or photomultiplier tube releases charge carriers or changes current, producing a signal (voltage or current) that can be measured and quantified. This electrical signal is what instrumental readouts display as the amount of light detected.

The monochromator’s role is to select a specific wavelength band of light for measurement; it doesn’t convert light to electricity. Light refers to the photons themselves, the energy entering the system. The flame can be a light source or a sample in flame-based techniques, but it isn’t the sensor either. So the detector is the component that converts photons into an electrical signal for measurement.