Short Answer
Inelastic scattering where a photon excites a vibrational mode and a red-shifted (Stokes) photon is emitted is the best answer.
Wave and optics questions test how frequency, wavelength, phase, interference, and geometry fit together. Start with the physical picture before choosing the equation.
SRS: incident photon excites a molecular vibration and is downshifted (Stokes shift); the process is stimulated (coherent amplification) at high intensities.
Why This Answer Is Correct
This is a Hard-level question in Waves & Optics. The prompt is really testing whether you can connect the concept to its defining physical relationship instead of picking a nearby-but-wrong term.
If a waves question feels messy, sketch the geometry or phase relationship first, then return to the algebra.
Choices At A Glance
- A. Elastic scattering of photons
- B. Inelastic scattering where a photon excites a vibrational mode and a red-shifted (Stokes) photon is emitted
- C. Fluorescence emission
- D. Two-photon absorption
When similar options appear on an exam, eliminate the ones that break the core law, use the wrong units, or confuse a definition with a consequence.
Topic Snapshot
Topic: Waves & Optics
Difficulty: Hard
Best next move: Re-state the governing law in your own words, then solve one more example from the same topic before moving on.