Which instrument is used for excitation by electromagnetic radiation?

• A. Fluorometer
• B. AES
• C. AAS
• D. Flame photometer

Answer: (A)

Excitation by electromagnetic radiation is the hallmark of fluorescence spectroscopy. A fluorometer uses a light source to deliver photons at a chosen excitation wavelength to the sample, promoting fluorophores to excited states. When they relax back, they emit light at a longer wavelength, which the instrument detects. This direct use of EM radiation to excite the sample is what makes a fluorometer the correct choice.

The other instruments rely on different energy inputs or measurement principles. Atomic emission spectroscopy uses electrical energy (arc, spark, or plasma) to excite atoms and then analyzes the emitted light. Atomic absorption spectroscopy measures how much of a specific illumination is absorbed as it passes through the sample, without relying on emission from excited states. A flame photometer detects light emitted from species in a flame, where excitation is primarily thermal rather than driven by an external light source.