Difference Between Fluorescence And Phosphorescence With Examples

Fluorescence and phosphorescence are two mechanisms that emit light or examples of photoluminescence. However, the two terms don’t mean the same thing and don’t the same thing and don’t occur the same way. In both fluorescence and phosphorescence, molecules absorb light and emit photons with less energy (longer wavelength), but fluorescence occurs much more quickly than phosphorescence and does not change the spin direction of the electrons.  Unlike phosphorescent products, fluorescent pigments stop glowing once the light source is removed.   

What Is Fluorescence?

Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength and therefore lower energy, than the absorbed radiation.

In fluorescence, an electron is raised from a certain baseline energy known as ground level to an excited level by a light photon or other radiation. Transition of the electron back to the ground level can occur spontaneously with radiation of the same energy as that which was absorbed.

The most common example of fluorescence occurs when the absorbed radiation is in the ultraviolet region of the spectrum and thus invisible to the human eye, while the emitted light is in the visible region, which gives the fluorescent a distinct color that can be seen only when exposed to UV light.

Fluorescent materials cease to glow nearly immediately when the radiation source stops, unlike phosphorescent materials, which continue to emit light for some time after.

What You Need To Know About Fluorescence

• Fluorescence is the absorption of energy by atoms or molecules followed by immediate emission of light or electromagnetic radiation.
• The emission of radiation or light suddenly stops on removal of source of excitation.
• In Fluorescence, the excited atom has comparatively short life time before its transition to low energy state.
• The time period or interval between the absorption and emission of energy is very short.
• 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.
• The emitted photon (light) has lower energy than the absorbed photon and emission occurs at a longer wavelength than the incident light.
• In fluorescence materials, gives an ‘’an immediate flash or afterglow’’ on excitation.
• Examples of Fluorescence: Gemstones fluoresce, including gypsum, talc, jelly fish, chlorophyll extract, vitamins etc. 

What Is Phosphorescence?

Phosphorescence is the absorption of energy by atoms or molecules followed by delayed emission of electromagnetic radiation. In other words, it is emission of light from a substance exposed to radiation and persisting as an afterglow after the exciting radiation has been removed.

In phosphorescence, light is absorbed by a material, bumping up the energy levels of electrons into an excited state. However, the energy of the light doesn’t quite match up with the energy of allowed excited states, so the absorbed photons get stuck in a triplet state. Transitions to a lower and more stable energy state take time, but when they occur, light is released. Because this release occurs slowly, a phosphorescent material appears to glow in the dark.

 Phosphorescence releases the stored energy slowly over time. Basically, phosphorescent material is ‘’charged’’ by exposing it to light. Then the energy is stored for a period of time and slowly released.

What You Need To Know About Phosphorescence

• It is the absorption of energy by atoms or molecules followed by delayed emission of electromagnetic radiation.
• The emission of radiation remains for some time even after the removal of source of excitation.
• In Phosphorescence, the excited atom has comparatively long life time before its transition to low energy state.
• The time period or interval between the absorption and emission of energy is comparatively long.
• Phosphorescence involves the transition from the single ground energy state to excited triplet state and involving a change of spin state.
• The emitted photon (light) has lower energy than the absorbed photon and emission occurs at a longer wavelength than fluorescence.
• Phosphorescent materials appears to ‘’glow in the dark’’, because of slow emission of light over time.
• Examples of phosphorescence: Glow-in-dark-stars, some safety signs and glowing paint etc.

Difference Between Fluorescence And Phosphorescence In Tabular Form

Conclusion

Both fluorescence and phosphorescence are spontaneous emissions of electromagnetic radiation. The difference is that the glow of fluorescence stops right after the source of excitatory radiation is switched off whereas for phosphorescence, the glow does not stop after the source of excitatory radiation is switched off. The glow continues for durations of fractions of a second up to hours.