Question

What is the difference between fluorescence and phosphorescence?

Short answer

Fluorescence is the instantaneous emission of absorbed radiation.

Phosphorescence is the absorption of energy by atoms or molecules following a delayed emission of light or electromagnetic radiation.

Step-by-step solution

Fluorescence

The electrons in an atom or molecule can absorb energy in electromagnetic radiation and thus excite to the upper energy state. This upper energy state is unstable; therefore the electron likes to return to the ground state. On return, it emits an absorbed wavelength In this process of relaxation, they emit excess energy like photons. This process of relaxation is called fluorescence. Fluorescence took place much faster. Generally, it ends in about $10-5$ seconds or less of time from the moment of excitation.

Phosphorescence:

When molecules absorb light and go into an excited state have two possibilities. They can either release energy and immediately return to baseline or undergo other non-radiation processes. If an excited molecule undergoes a non-radiation process, it emits some energy and comes to a triplet state in which the energy is slightly less than the energy of the exited state, but is higher than the energy of the ground state. Molecules can stay a little longer in this triple state with less energy.