Question

What is the distinction between fluorescence and phosphorescence?

Answer 1

1> Fluorescence and phosphorescence both are photoluminescence process which means the phenomena of absorption and subsequent emission of light by a substance.

2>

When light is supplied to a sample of Molecules, we immediately see the Fluorescence. Fluorescence stops as soon as we take away the light source. But Phosphorescence tends to stay little longer even after the irradiating light source is removed.

3>Fluorescence take place when the Molecules come back to the ground state from the singlet-excited stage, so the decay period is very low. In Phosphorescence molecules goes to singlet exited state, it first dissipate its energy and then transit to triplet state. Then form triplet state molecule jump back to ground. So, the decay period is longer.

4>

The energy released in the Fluorescence process is higher than that in the Phosphorescence.

Example of fluorescent material are crude oil, anthracene

Example of phosphorescent materials are the glow in the dark toys, paint and clock dials.