Question

Main difference between fluorescence and phosphorescence

Answer 1

Fluorescence

Phosphorescence
F#
It is the absorption of energy by atoms or molecules followed by immediate emission of light or electromagnetic radiation
P#
It is the absorption of energy by atoms or molecules followed by delayed emission of electromagnetic radiation
F#
The emission of radiation or light suddenly stops on removal of source of excitation
P#
The emission of radiation remains for some time even after the removal of source of excitation
F#
In Fluorescence, the excited atom has comparatively short life time before its transition to low energy state
P#
In Phosphorescence, the excited atom has comparatively long life time before its transition to low energy state
F#
The time period or interval between the absorption and emission of energy is very short
P#
The time period or interval between the absorption and emission of energy is comparatively long
F#
Absorption process occurs over short time interval and involves the transition from ground state to singlet excited state and do not change the direction of the spin.P#
Phosphorescence involves the transition from the single ground energy state to excited triplet state and involving a change of spin state
F#
The emitted photon (light) has lower energy than the absorbed photon and emission occurs at a longer wavelength than the incident light
P#
The emitted photon (light) has lower energy than the absorbed photon and emission occurs at a longer wavelength than fluorescence
F#
In fluorescent materials, gives an‘an immediate flash or afterglow’on excitation
P#
Phosphorescent materials appears to'glow in the dark',because of slow emission of light over time.

Examples of Fluorescence:

Gemstones fluoresce, including gypsum, talc.

Jelly fish, chlorophyll extract, vitamins etc

Examples of Phosphorescence:

Glow of clock dial or toys or in bulbs after switching off the light in the room. The glow remains for some minutes or even hours in a dark room

Phosphorescent materials in sign board illuminate during night.