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Interaction of Light With Mater

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University of Duhok
College of Sincse
Physics Department
Interaction of Light
with Matter
How does photon interact with mater?
Prepared by group B6
- Partizan Fariq
- Awaz Mohamed
- Heleen Nawzad
- Rojman Kamal
- Basma Lawrance
- Halat
Supervised By :
Dr. Mohamed Ibrahim
Light and Matter
• Three ways light interacts with matter
 Reflection
 Transmission
(Refraction)
Absorbtion
Reflection and Refraction
Interaction of photon with matter
(Absorbtion and scattering)
# COHERENT SCATTERING
• Is also known as classical scattering
or Rayleigh scattering.
• In coherent scattering :
Low energy rediation encounter
electrons
Electrons are set into vibration
Vibrating electrons, emits rediation
Atom returns to it’s undisurbed state
#Compton Scattering
•
discovered by Arthur Holly Compton, is the scattering of
a photon by a charged particle, usually an electron. It results in a
decrease in energy (increase in wavelength) of the photon called
the Compton effect. Part of the energy of the photon is
transferred to the recoiling electron.
#Photoelectric effect
• Definition : the phenomenon of emission of electrons by
the metals when they are exposed to light of suitable
frequency is called as the photoelectric effect and
emitted electrons are called as photoelectrons.
#Pair Pruducrion
• Pair pruducrion is a
phenomena in wich a
photon with energy
more that 1.022 MeV
converted into an
electron and positron
when it passes near
a nucleus of an atom
What Happens to the matter when a
photon interact with it?
• Excitation: when a photon falls on an electron
with the energy equal to the difference between
two energy levels, the electron absorb the photon
and jumps to higher energy state, this
phenomenon called excitation. Then the electron
de-excitation to it’s stat emitting a photon with
same energy of absorbed photon .
• This is also called scattering
• Ionization: when the photon has that energy
to eject an electron from the atom, the atom
loss an electron and become a positive ion,
. this process called Ionization by photons.
• Heat:
• When light energy hits an object, some of
the energy is absorbed by the object. This
energy makes the molecules of the object
vibrate faster. If we touch the object, we feel
this vibration as heat.
Thanks for listening
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