Which instrument measures the light intensity emitted at a longer wavelength after the analyte absorbs light at a specific wavelength?

Which instrument measures the light intensity emitted at a longer wavelength after the analyte absorbs light at a specific wavelength?

• A. Photometer
• B. Atomic absorption spectrophotometer
• C. Fluorometer
• D. Nephelometer

Answer: (C)

Fluorescence detection. When the analyte absorbs light at a specific wavelength (excitation), it can relax by emitting light at a longer wavelength. A fluorometer is built to measure exactly that emitted light, using an excitation source and a detector tuned to capture the longer-wavelength emission. This separation of excitation and emission wavelengths, and the measurement of emitted fluorescence intensity, is what distinguishes fluorometry from other optical methods. In contrast, a photometer typically measures how much light is transmitted or absorbed at a given wavelength, not the emitted light; an atomic absorption spectrophotometer analyzes absorption by atoms in vapor form for elemental analysis; a nephelometer measures light scattered by particles.

Fluorescence detection. When the analyte absorbs light at a specific wavelength (excitation), it can relax by emitting light at a longer wavelength. A fluorometer is built to measure exactly that emitted light, using an excitation source and a detector tuned to capture the longer-wavelength emission. This separation of excitation and emission wavelengths, and the measurement of emitted fluorescence intensity, is what distinguishes fluorometry from other optical methods.

In contrast, a photometer typically measures how much light is transmitted or absorbed at a given wavelength, not the emitted light; an atomic absorption spectrophotometer analyzes absorption by atoms in vapor form for elemental analysis; a nephelometer measures light scattered by particles.