What device is used to modulate the light source in atomic absorption spectrophotometry?

• A. Chopper
• B. Monochromator
• C. Detector
• D. Filter wheel

Answer: (A)

The light modulation is achieved by a device that periodically interrupts the beam, creating a repeating on-and-off pattern. This modulation lets the detector system lock in to a specific frequency, so the signal from the absorbed light stands out against noise and drift. That improves sensitivity and signal-to-noise ratio in atomic absorption measurements, where tiny changes in light transmitted through the sample need to be detected precisely.

The monochromator’s job is to select the exact wavelength to monitor, not to modulate the light. The detector is the sensor that converts light into an electrical signal, but it does not modulate the light itself. The filter wheel changes spectral components or reference signals, but it isn’t used to modulate the light intensity at a known frequency in standard operation.

So, the device used to modulate the light source is the one that periodically blocks and unblocks the beam, producing a modulated signal for improved detection.