What is the Difference Between Fluorescence and Phosphorescence and Luminescence?

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Fluorescence and phosphorescence are both forms of photoluminescence, which involves the absorption of light and the subsequent emission of light at a longer wavelength and lower energy. The main difference between the two lies in the time it takes for the emitted light to decay after the initial absorption of light.

Fluorescence:

  • Occurs very shortly after photoexcitation of a substance.
  • The emission of light is immediate and only visible as long as the excitation source is present.
  • Examples of fluorescence include gemstones, jellyfish, and chlorophyll extract.

Phosphorescence:

  • Continues long after the photoexcitation has ceased.
  • The material can store the absorbed energy and release it later, resulting in an afterglow that persists after the light has been switched off.
  • Examples of phosphorescence include glow-in-the-dark toys, clock dials, and emergency exit signs.

In summary, the primary difference between fluorescence and phosphorescence is the duration of the emitted light after the initial absorption of light. Fluorescence involves an immediate emission of light that disappears as soon as the excitation source is removed, while phosphorescence involves a delayed emission of light that persists even after the excitation source has been removed.

Comparative Table: Fluorescence vs Phosphorescence vs Luminescence

Fluorescence, phosphorescence, and luminescence are related phenomena involving the emission of light from certain materials. Here is a comparison table highlighting the differences between these terms:

Property Fluorescence Phosphorescence Luminescence
Definition Fluorescence is the emission of light by an object exposed to electromagnetic radiation. Phosphorescence is the continued emission of light without heat after exposure to and removal of a source of electromagnetic radiation. Luminescence is the emission of light produced by means other than heat.
Excitation Instantaneous phenomenon, with photon energy absorbed and immediately re-emitted as radiation of a different frequency. Longer-lived excited state, with a timescale ranging from seconds to minutes. Varies depending on the type of luminescence (e.g., chemiluminescence, bioluminescence).
Timescale Short-lived, with excited state lasting less than 10^-5 seconds. Longer-lived, with excited state lasting from seconds to minutes. Varies depending on the type of luminescence.
Energy Transition Electronic energy transition results in short-lived electrons in the excited state of fluorescence. Change in electron spin results in a longer lifetime of the excited state. Varies depending on the type of luminescence.
Emission Emission spectrum occurs at longer wavelength than the excitation radiation. Emission spectrum occurs at longer wavelength than the excitation radiation. Varies depending on the type of luminescence.

In summary, fluorescence and phosphorescence are types of photoluminescence, with the main difference being the timescale of the excited state and the energy transition involved. Luminescence is a broader term encompassing various forms of light emission, including fluorescence, phosphorescence, chemiluminescence, and bioluminescence.