The document discusses photoluminescence, focusing on fluorescence and phosphorescence, outlining their principles, applications, and examples of fluorescent materials. Fluorescence occurs when a substance absorbs energy and re-emits it almost immediately, while phosphorescence involves a delayed light emission after the energy source is removed. Practical applications include uses in biology, mineralogy, and various consumer products like lamps and safety signs.

1. PRESENTED BY
ATIKUR RAHMAN
Department of Optometry, RIPANS

2. CONTENTS:
 Photoluminescence
 Fluorescence
 Energy level diagram
 Application of fluorescence
 Fluorescent materials
 Fluorescent lamp
 Phosphorescence
 Principle of phosphorescence
 Application of phosphorescence
 References

3. PHOTOLUMINESCENCE
 It is a process where a substance absorbs photons
and then re- emits them.
TYPES:
 Fluorescence
 phosphorescence

4. FLUORESCENCE
 It is the emission of electromagnetic radiation,
caused by excitation of atoms in a material, which
then re-emit almost immediately (within about 10−8
sec.)
 The initial excitation is usually caused by absorption
of energy.
 Emission of light suddenly stops on removal of
source of excitation.

7. ENERGY LEVEL DIAGRAM
 Transition occurs from ground to single excited state.

9. APPLICATION :
 To identify structures in fixed and live biological
samples.
 Fluorescence has many practical applications,
including mineralogy, medicine, chemical
sensors(fluorescence spectroscopy), fluorescent
labelling, dyes, biological detectors and cathode-ray
tubes.
 X- ray fluorescence is used to analyze minerals.

12. FLUORESCENT MATERIALS
 The substance that
fluoresces is called
fluorescent material.
 Calcite
 Agrellite
 Apatite.
 Aragonite.
 Baryte.
 Cerussite

13. FLUORESCENT LAMP
 Fluorescent lamps are
lamps which emit
fluorescent light, usually
generated by irradiation
of a phosphor with light
from an electric gas
discharge.

14. PHOSPHORESCENCE
 Phosphorescence is the light energy emitted by a
certain form of chemical reaction in which the
reactants excess chemical energy is release as light
energy.
 It persists as an afterglow when the exciting is
removed.

17. PRINCIPLE OF
PHOSPHORESCENCE
 Any material observed light and enter in excited
state, then the emission of energy from triplet state
to ground singlet state is phosphorescence

18. APPLICATION
•Toys
•Watches
•Switches
•Safety signs
•Paints and markings
•Make-ups