Physics

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Physics

• Conf. Dr. Radu Fechete
• Technical University of Cluj-Napoca

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Content 1

• Davisson-Germer experiment
• Barrier of potential. Tunnel effect
• The Hydrogen atom
• Quantum numbers
• Stern and Gerlach experiment
• Atomic orbitals
• Atomic spectra
• Holography

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Davisson-Germer experiment
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Barrier of potential. Tunnel effect


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The Hydrogen atom

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Quantum numbers


n principal quantum numbers l orbital
quantum number m magnetic quantum number
Bohr magneton
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Stern and Gerlach experiment
Energy of a magnetic moment in B
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Atomic orbitals
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Atomic spectra
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Atomic spectra

The theory of quantum transitions
-wave number

Rydberg consntant


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LASERs
Def light amplification by stimulated emission
of radiation
Probability of spontaneous emission
Probability of spontaneous absorption
Boltzmann distribution

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Holography
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Content 2

• Semiconductors
• Hall Effect
• Difference of potential at metal-metal contact
• Thermoelectric effect (Seebeak effect)
• Magnetic materials
• Diamagnetism
• Paramagnetism
• Ferromagnetism
• Superconductivity

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Energetic Bands in solids
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Semiconductors
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Hall Effect
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Difference of potential at metal-metal contact
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Thermoelectrically effect (Seebeck effect)
Thermoelectrically effect consist in the
apparition of an electromotive tension into a
two-metals electrical circuit when a difference
of temperature exist between those two contact
points.
The Peltier effect is considered the inverse of
thermoelectric effect consisting in the heat
radiation while an electrical current passes
through an electical circuit consisting from two
different materials
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Magnetic properties of materials
The total magnetic moment
Sample magnetization
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Magnetic properties of materials
H magnetic field intensity ?m magnetic
susceptibility ?r material relative magnetic
permeability ? material magnetic permeability
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Substances classification

• Diamagnetic (?m lt 0 small ?m ? ?m(T))
• Paramagnetic (? m gt 0)
• Paramagnetic (? m gt 0 small - Curie law)
• Ferromagnetic (? m gt 0 large ? m ? m(T))
• Antiferromagnetic
• Ferrimagnetic.

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Magnetic materials Diamagnetism
The materials with no permanent magnetic moments
are diamagnetic materials. The diamagnetism
originates in the change of the electrons orbit
in the presence of the external magnetic field.
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Paramagnetic materials
Curie law
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Ferromagnetic materials
Ferromagnetic materials are characterized by
magnetic memory Hysteresis curves.
Hc coercitive fields Bs saturation field Br
remanent magnetization
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Ferromagnetic materials
Due to the reorientation of elementary magnetic
moments the sample magnetization increases with
the increase of the external magnetic
field. Barkhausen effect the increase of
magnetization appears in steps.
Curie-Weiss law
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Magnetic materials
Paramagnetic Ferromagnetic Antiferromagnetic
Ferrimagnetic Forced ferromagnetic
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Superconductivity

• An element (inter-metallic alloy, ceramics etc.)
  that will conduct electricity below a certain
  temperature without resistance.

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Superconductor materialTypical structure
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Superconductivity Meissner effect
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The origin of superconductivity Cooper pairs
John Bardeen, Leon Cooper si Robert Schrieffer
(BCS theory), after 60 years from the discovery
of the supra-conductibility phenomena, assumes
that the Cooper pairs are now bosons and are no
longer subjected to the Pauli principle of
exclusion. The electrons motion inside of
superconductor material is perfectly ordered and
the interaction with the network is much reduced.
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Thank You for your attention