Physics Conf. Dr. Radu Fechete Technical University of Cluj-Napoca.
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Transcript of Physics Conf. Dr. Radu Fechete Technical University of Cluj-Napoca.
PhysicsPhysics
Conf. Dr. Radu FecheteConf. Dr. Radu Fechete
Technical University of Cluj-NapocaTechnical University of Cluj-Napoca
Content 1Content 1
Davisson-Germer experimentDavisson-Germer experiment Barrier of potential. Tunnel effectBarrier of potential. Tunnel effect The Hydrogen atomThe Hydrogen atom Quantum numbersQuantum numbers Stern and Gerlach experimentStern and Gerlach experiment Atomic orbitalsAtomic orbitals Atomic spectraAtomic spectra HolographyHolography
Davisson-Germer experimentDavisson-Germer experiment
Barrier of potential. Tunnel effectBarrier of potential. Tunnel effect
l
l
xptU
xptU
xptU
.0
0.0
0.0
tcoefficienontransmissiC
CT
tcoefficienreflexionC
CR
I
III
I
I
2
1,
2
1,
2
1,
2
2,
lEUm2
2
2
2
e1n
n16T
E
EUn
2x
1x
EUm22
eTdx
The Hydrogen atomThe Hydrogen atom
0rUEm2
dz
d
dy
d
dx
d2
e2
2
2
2
2
2
,frR,,r ,f
0rUEm2
sin
1sin
sin
1
rr
rr
12
e2
2
22
2
im212
1n0
mm, ecose
!ml!lnn8
!ml!mln1l2
na
11,,r m
lll
lln, PL
2220
4e
n nh8
emE
12
1nllL
m
m
m2m2
d
d1 PPm
l
Laguerre polynomial Legendre polynomial Quantified energy
Quantum numbersQuantum numbers
im212
1n0
mm, ecose
!ml!lnn8
!ml!mln1l2
na
11,,r m
lll
lln, PL
1 llL
mzLL2me
e
m
2me
L2me
ee
zz
20 Am24-
e
109.27322me
n – principal quantum numbersl – orbital quantum number
m – magnetic quantum number
Bohr magneton
Stern and Gerlach experimentStern and Gerlach experiment
BU
z
B
z
UF
zzz
Energy of a magnetic moment in B
Spin quantum number
2
1zS
Atomic orbitalsAtomic orbitals
Atomic spectraAtomic spectra
Atomic spectraAtomic spectra
1~
~cc
-wave number The theory of quantum transitions
2220
42
8 nh
eZmE en
22
0
4
8 h
eme
2
2
n
ZEn
222 11~
nmZhch
222 11~
nmZH
Rydberg consntant
H= 1.0967758 107 m-1
= 2.15 10-18 J = 13.6 eV
LASERsLASERsDef: light amplification by stimulated emission of radiation
nnmsp,em NAP
uNBP mmnst,abs
m
n
mn
nmmmnnnmst,abssp,em N
N
B
AuuNBNAPP
Tk
E
0nB
n
eNN
Probability of spontaneous emission
Probability of spontaneous absorption
Boltzmann distribution
uNBP nnmstim,em
uNBNAP nnmnnmem
nmTk
h
mn
nmabsem
BeB
AuPP
B
1
18,
3
3
Tk
h
Bec
hTu
Probability of stimulated emission
HolographyHolography
Content 2Content 2
SemiconductorsSemiconductors Hall EffectHall Effect Difference of potential at metal-metal contactDifference of potential at metal-metal contact Thermoelectric effect (Seebeak effect)Thermoelectric effect (Seebeak effect) Magnetic materialsMagnetic materials
DiamagnetismDiamagnetismParamagnetismParamagnetismFerromagnetismFerromagnetismSuperconductivitySuperconductivity
Energetic Bands in solidsEnergetic Bands in solids
Semiconductors:Semiconductors:
Hall EffectHall Effect
a
IBHR
a
IB
ne
1HU
2e
nh
pe
2e
n2h
p
HR
Difference of potential at metal-Difference of potential at metal-metal contactmetal contact
2
1B0102c n
nln
e
Tk
e
LLU
Thermoelectrically effect Thermoelectrically effect (Seebeck effect)(Seebeck effect)
2
1BA n
nlnTT
e
KE
BA TTE
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: tIbQ
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.
Magnetic properties of materialsMagnetic properties of materials
mi
N
1iii
N
1ii SIm
M
The total magnetic moment
V
SI
V
m
V
N
1iii
N
1ii
MM
Sample magnetization
Magnetic properties of materialsMagnetic properties of materials
MHB 00
HM m
mr 1
H – magnetic field intensitym – magnetic susceptibilityr – material relative magnetic permeability – material magnetic permeability
r0
Substances classificationSubstances classification
Diamagnetic: (Diamagnetic: (mm < 0 – small; < 0 – small; mm mm(T))(T))
Paramagnetic (Paramagnetic ( mm > 0) > 0)Paramagnetic: (Paramagnetic: ( mm > 0 – small; - Curie law) > 0 – small; - Curie law)
Ferromagnetic (Ferromagnetic ( mm > 0 – large; > 0 – large; mm = = mm(T))(T))AntiferromagneticAntiferromagneticFerrimagnetic.Ferrimagnetic.
Magnetic materials: DiamagnetismMagnetic 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.
Paramagnetic materialsParamagnetic materials
T
C Curie law
Ferromagnetic materialsFerromagnetic materials
Ferromagnetic materials are characterized by magnetic memory: Hysteresis curves.
Hc – coercitive fieldsBs – saturation fieldBr – remanent magnetization
Ferromagnetic materialsFerromagnetic 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.
CT
C
Curie-Weiss
law
Magnetic materialsMagnetic materialsParamagnetic
Ferromagnetic
Antiferromagnetic
Ferrimagnetic
Forcedferromagnetic
SuperconductivitySuperconductivityAn element (inter-metallic alloy, ceramics etc.) that An element (inter-metallic alloy, ceramics etc.) that will conduct electricity below a certain temperature will conduct electricity below a certain temperature without resistance. without resistance.
Superconductor material:Superconductor material:Typical structureTypical structure
Superconductivity : Superconductivity : Meissner effectMeissner effect
The origin of superconductivity The origin of superconductivity Cooper pairsCooper 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.
Thank You for your attentionThank You for your attention