Why does fluorescence glow at longer wavelength than the driving light?

• The molecule absorbs twice before emitting
• Some energy drains as heat before emission
• The lamp changes colour inside the sample

Which steps of the Jablonski diagram trade photons?

• Internal conversion and vibrational relaxation
• Absorption, fluorescence and phosphorescence
• Crossing to the triplet only

Internal conversion and crossing to the triplet emit photons.

Which of two dyes fluoresces more strongly?

• The floppy, twisting one with broken conjugation
• The rigid, flat, conjugated one
• Both glow exactly equally

A dye glows weakly in warm solvent but brightly when frozen in a film. Why?

• Freezing creates new electrons in the dye
• Cold light is always brighter than warm light
• Free rotation opens heat paths, and freezing blocks them

Why is phosphorescence slow?

• Its spin flip is forbidden
• Triplet molecules move very slowly
• Phosphorescence uses heavier photons

A student labels crossing to the triplet as a glowing step. What is the error?

• Crossing emits the brightest light of all
• Crossing is a silent heat step with no photon
• Labels never matter in diagrams

A heavy atom is built into a glowing molecule. What changes, and why?

• Fluorescence stops because heavy atoms absorb all light
• Nothing changes, mass never matters
• Phosphorescence speeds up as the spin ban loosens