3. INTRODUCTION – The Word Luminescence was first used by a German
physicist EILHARDTWIEDEMANN ,In 1888 in Latin
. ‘ Lumen’ means ‘ light’ The material or phosphorsMeaning
Light Bearers in Greek. Luminescence is spontaneous Emission of light by
A substance .
5. ELECTRO LUMINESCENCE
Electro Luminescence is an
Optical Phenomenon and
electrical Phenomenon in
which a Material Emits light
in Response to the Passage of
an Electric current or to a
strong electric field .
Electroluminescence is a non
Thermal Generation of light
6. PHOTO LUMINESCENCE
The phenomenon of temporary light
Absorption and Subsequent light
emission is called photo
Luminescence. Photo Luminescence is
a process in which Molecule Absorbs
a photon in the visible Region
excited one of it electron to A higher
electronic exited state and then
Radiates a photon as the electron
Returns to alower energy state .
7. TYPE OF PHOTO LUMINESCENCE
FLUORESCENCE – It Is Absorption of Energy by Atom or
Molecules followed by immediately Emission of
light Electromagnetic radiation .The emission of Radiation or light
suddenly stop on Removal of source of excitation . It is form of
Luminescence in most case the emitted light has a longer wavelength
and therefore lower Energy than the Absorbed Radiation
PHOSPHORESCENCE- It is the Absorption of energy by
atom or molecules followed by Delayed
Emission of light Electromagnetic radiation. The emission of Radiation
Remain for some time even after Removal of source of excitation .The
Emitted photon has lower energy than the Absorbed photon and
emission at a Longer wavelength than florescence .
8. ADVANTAGES
1. High sensitivity
2. Good Energy Response
3. Reusability
DISADVANTAGES
1. Not Advisible for Radioactive elements
2. Neutron Dosimetry problem
3. Difficult to study complex system
