Most atomic absorption spectrophotometers incorporate a beam chopper and a tuned amplifier. The purpose of these components is to avoid errors that would be caused by

Most atomic absorption spectrophotometers incorporate a beam chopper and a tuned amplifier. The purpose of these components is to avoid errors that would be caused by

• A. Variations in flame temperature
• B. Deterioration of the hollow-cathode lamp
• C. Stray light from the hollow-cathode lamp
• D. Measurement of light emitted by the analyte

Answer: (D)

The main idea is that the beam chopper and a tuned amplifier (lock-in type) are used to separate the true signal of light transmitted from the lamp through the sample from unwanted light that could come from the analyte itself. In atomic absorption, you want to measure how much lamp light is absorbed by atoms in the sample, not any light the excited atoms might emit. By chopping the lamp light at a known frequency, the detector sees a signal that fluctuates at that frequency. The tuned amplifier then only boosts signals at that specific frequency and rejects all other, non-synchronous light. Light emitted by the analyte doesn’t follow the chopped source, so it isn’t amplified the same way and therefore doesn’t distort the absorption measurement. That’s why this arrangement helps avoid errors caused by light emitted by the analyte.

The main idea is that the beam chopper and a tuned amplifier (lock-in type) are used to separate the true signal of light transmitted from the lamp through the sample from unwanted light that could come from the analyte itself. In atomic absorption, you want to measure how much lamp light is absorbed by atoms in the sample, not any light the excited atoms might emit. By chopping the lamp light at a known frequency, the detector sees a signal that fluctuates at that frequency. The tuned amplifier then only boosts signals at that specific frequency and rejects all other, non-synchronous light. Light emitted by the analyte doesn’t follow the chopped source, so it isn’t amplified the same way and therefore doesn’t distort the absorption measurement. That’s why this arrangement helps avoid errors caused by light emitted by the analyte.