Download P3A3B Atomic Physics Notes 2013

P3A3B Atomic Physics Notes 2013
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Coghlan
Atomic Physics Notes
Light is an example of _____________
radiation which transfers _____________
at 3.00 x 108 m s-1.
The electromagnetic
_____________ is the _____________ of
all _____________ of this type.
A ray or beam of light actually consists
of two _____________ fields –
_____________ and _____________ – hence
– electromagnetic.
These two fields are
_____________ at _____________ angles.
Its _____________ is the length of one
oscillation or _____________ or energy
pulse.
Its _____________ is how many times
the _____________ oscillate per second.
http://micro.magnet.fsu.edu/primer/java/polarizedlight/emwave/
http://www.colorado.edu/physics/2000/microwaves/water_rotates.html
P3A3B Atomic Physics Notes 2013
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Electromagnetic
radiation
Coghlan
Production
radio waves
e- _____________ up and down a radio mast
micro waves
e- oscillating in a _____________ cavity
(magnetron)
IR, visible, UV e- oscillating within _____________ &
_____________
X-rays
e- rapidly _____________
gamma rays
e- oscillating in the _____________
http://lectureonline.cl.msu.edu/~mmp/applist/Spectrum/s.htm
Nature of Light
Wave Particle Duality
http://www.colorado.edu/physics/2000/schroedinger/two-slit3.html
Newton
 1671
 _____________ model for light
 light behaves like a _____________ _____________
 explains most properties of light except _____________ and
interference
Huygens
 1678
 wave model
http://www.colorado.edu/physics/2000/schroedinger/two-slit2.html
Young
 1801
 double slit _____________ experiment supported the wave model
Maxwell
 1865 - complete wave theory for light
 extended to all _____________ radiation
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Photoelectric effect
http://www.colorado.edu/physics/2000/quantumzone/photoelectric.html
The Photoelectric effect is the
_____________ of an e- from a
_____________ (usually metal)
when _____________ radiation
(usually light) shines on it.
For the photoelectric effect, the following observations were made;
-
there is a certain _____________ frequency below which no
_____________ were emitted
-
_____________ the threshold frequency, the _____________ the light
the more photoelectrons emitted
-
there was no time de_____________ lay between irradiation and
_____________
-
if f is increased, EK of the _____________ increases
The wave model was _____________ in explaining the photoelectric
effect!
If the wave model is true, then
X
-
any frequency light should cause photoemission -
-
for lower frequencies there should be a time delay between
irradiation and photoemission -
-
X
the brighter the irradiation, the more the photoelectrons –
X.
P3A3B Atomic Physics Notes 2013
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Coghlan
Max Planck
 1900
 light energy is not _____________
 light energy is delivered in tiny, _____________ bundles of energy
called _____________ or _____________
 the energy of the photon is _____________ to its frequency.
Where
E=hf
E  energy, J
h  Planck’s constant, 6.63 x 10-34 J s
f  frequency of photon, Hz
The current view of light is that it possesses both _____________ and
_____________ properties and which properties light in fact exhibits
depends on the _____________ used to look at it.
Atomic Structure
http://www.rsc.org/chemsoc/timeline/pages/1911.html
http://www.walter-fendt.de/ph14e/bohrh.htm
http://www.colorado.edu/UCB/AcademicAffairs/ArtsSciences/physics/PhysicsInitiative/Physics2000/a
pplets/a2.html
http://csep10.phys.utk.edu/astr162/lect/light/bohr.html
Neils Bohr
 1913
 e- exist in atoms in _____________ levels n = 1, 2, 3, 4……
 the energy of the e- is _____________ – it can only have
_____________ values
 e- in one energy level can jump to another level by the
_____________ or _____________ of a _____________
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 the energy of such a photon =  E between the _____________ levels
 lowest energy _____________ for an atom is called its
_____________ state
 any other electron _____________ for an atom is its _____________
state.
http://www.physics.uoguelph.ca/applets/Intro_physics/kisalev/java/atomphoton/index.html
Consequently, an e- in an atom may _____________ from a _____________
allowed energy level to a lower one by _____________
just the
_____________ amount(quantum)of energy (photon).
LINE EMMISION SPECTRUM
http://csep10.phys.utk.edu/astr162/lect/light/absorption.html
http://jersey.uoregon.edu/elements/Elements.html
Such _____________ emission spectra are _____________ for every
elemental gas because every element has its own particular set of
_____________ energy _____________ and hence only certain energy
_____________ are _____________ from the excited atom.
http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/linesp16.swf
Ex/ How many emission lines in a line emission
spectrum would be produced by a gaseous atom
excited by an electric field if its available
energy levels are shown in the diagram?
Ground state electrons in such an electric field continually
_____________ just the right _____________ of energy to jump to a
P3A3B Atomic Physics Notes 2013
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higher _____________ state (an _____________ state) and then fall
back down to the _____________ state in one or more jumps from
allowed energy state to allowed energy state.
The ground state for valence electron represents a _____________
energy situation for an atom.
Energy
of
electron
0
Distance from
nucleus
The energy levels allowed for the electron to access can be
represented by a ladder diagram.
Ionisation
Many close levels
E4
E3
E2
E1
An atom in the ground state is an
_____________ atom.
If an
electron gains too much energy,
it will _____________ the atom
and an ion will be made.
E0 Ground state
Energy
is _____________ to excite the
atom.
Energy is _____________ as
_____________ when the excited
electron _____________ back down to the _____________ state.
http://www.colorado.edu/physics/PhysicsInitiative/Physics2000/quantumzone/bohr2.htm
l
 e- in an atom may _____________
level to a _____________
from a lower _____________
one by _____________
amount(quantum) of energy (_____________).
energy
just the correct
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LINE ABSORPTION SPECTRUM
http://www.colorado.edu/physics/PhysicsInitiative/Physics2000/quantumzone/lines2.ht
ml
Photon absorption
To become excited, a ground state electron may _____________ a
photon.
However a ground state electron will only _____________ a
photon if the photon’s energy _____________ corresponds to the energy
_____________ for that electron to jump to one of its _____________
higher states.
Ex/
A gaseous Hg atom is being irradiated with photons of many
different energies.
(a)
Ionisation
What energy photons may be
absorbed?
What energy photon causes
ionisation?
(c)
What frequency would the
-8.83 x 10-19 J
Ground state
photon in (b) possess?
(d)
-5.94 x 10-19 J
Energy of e-
(b)
0
-2.50 x 10-19 J
-16.6 x 10-19 J
What type of spectrum would be
produced by this situation?
(e)
Not counting the ionisation energy, how many lines would be
produced in the spectrum and what would be their colours?
http://www.physics.uoguelph.ca/applets/Intro_physics/kisalev/java/laser/
Electron bombardment(scattering)
http://www.matter.org.uk/tem/electron_scattering.htm
If an atom is bombarded with electrons, _____________ or
_____________ collisions between bombarding electrons and electrons
in the _____________ state may occur.
That is the bombarding
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electrons may give up _____________ or _____________ or _____________
of their EK and are then _____________ often with reduced EK.
Ex/
8.00 eV electrons bombard an atom in
Energy of e-
Ionisation
0
-1.80 eV
its ground state.
-2.10 eV
the scattered electrons, and
-4.70 eV
(b)
(a)
Calculate;
the energies and velocities of
the frequencies of the emitted
photons and their colours.
Ground state
Note:
-10.0 eV
E = V q
1.00 eV = 1.60 x 10-19 J
Mass of electron
= 9.12 x 10-31 kg
P3A3B Atomic Physics Notes 2013
Types of Spectra
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Coghlan
http://www.astrophys-assist.com/educate/solarobs/ses01p11.htm
There are three main types of spectra – _____________, _____________
and _____________ .
Continuous Spectrum
Line absorption
spectrum
Line emission
spectrum
Hot
Gaseous
element
Cool
Gaseous
element
energises
Hot source
Liquid or
Solid
energises
Hot
Gaseous
molecules
Cool coloured solution
or
transparent coloured
solid
Band absorption
spectrum
Band emission
spectrum
http://www.antarcticconnection.com/antarctic/weather/aurora.shtml
Spectral analysis
http://www.astro.uiuc.edu/~kaler/sow/spectra.html#absan
Each element has its own _____________ emission/absorption
_____________.
A mixture of elements generating an _____________
/_____________ spectrum will retain all the _____________ from each
element.
An atomic absorption _____________ can be used to obtain an
absorption spectrum from a sample and by _____________ lines,
_____________ the _____________ elements in the sample.
http://www.learner.org/teacherslab/science/light/color/spectra/
http://www.aurora-instr.com/ai1200.htm
P3A3B Atomic Physics Notes 2013
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The black Fraunhöfer lines seen in the sun’s _____________ spectrum
are caused by absorption of _____________ by _____________ in the
sun’s _____________.
Similar analysis can be performed for other
stars and also for planets using light from stars that just
_____________ a planet’s surface.
Luminescence
Luminescence is the _____________ of light by a _____________ not due
to the _____________ of the material.
Luminescence
caused by
photons
electrons
living
thing
chemical
reaction
Bioluminescence
Photoluminescence
Electroluminescence
may show
Chemiluminescence
may show
Fluorescence or Phosphorescence
The excited material emits one or more
photons in a very short period of time
( 10-8 s) and returns to ground state
producing a line or band emission
spectrum.
e.g. whiteners, fluorescent tube.
A phosphorescent material has a
metastable excited state in which the
excited electron remains in a higher
energy level for an extended period of
time (up to 8 hours). It produces a line
or band emission spectrum.
e.g. watch dials, TV screens, toys.
http://mineral.galleries.com/minerals/property/fluoresc.htm
P3A3B Atomic Physics Notes 2013
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http://www.lifesci.ucsb.edu/~biolum/
Coghlan
http://www.shsu.edu/~chm_tgc/chemilumdir/chemiluminescence2.html
Whiteners
http://www.seventhgeneration.com/household_hazards/optical_brighteners.php
Over time, _____________ paper and _____________ becomes more yellow.
Intensity
Old
Intensity
New
Red
Violet
Red
Frequency
Violet
Frequency
An _____________ brightener can return the yellow fabric to white
temporarily.
These optical brighteners (usually contained in
_____________ powder)are excited by _____________ radiation and when
the _____________ return to _____________ state, they primarily emit
_____________ in the blue-violet part of the spectrum and thus return
the _____________ spectrum and the fabric appears white again.
Energy of e-
Ionisation
Ground state
P3A3B Atomic Physics Notes 2013
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X-Rays
 Röentgen, 1895
 Produced in two ways.
(1)
High energy _____________ (> 40 keV) slowed down by
_____________ with a _____________ atom (high m.p.
metal) and being _____________ with a lower energy –
the energy _____________ equal to the
X-ray Intensity
energy of the X-ray _____________ produced.
Because many _____________ frequency X-ray
photons can be produced in this way, an Xray _____________ is _____________.
Wavelength
(2)
electron and _____________
from a _____________
falls into this
by the incident
X-ray Intensity
_ level electron excited
the atom.
The higher
An e-
energy level
_____________
lower energy level and an
_____________.
____________
X-ray photon is
Wavelength
_____________ is filled by _____________ e-.
energy level eBecause of the
_____________ of energy levels, only _____________ frequency Xrays can be generated in this way.
So a typical X-ray spectrum is a
_____________ spectrum with one or more
_____________ characteristic of the target
_____________.
http://www.colorado.edu/physics/PhysicsInitiative/Physics2000/xray/making_xrays.htm
l
P3A3B Atomic Physics Notes 2013
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 only  1% of incident e- produce X-rays, the _____________
appears as _____________.
 Much of the _____________ e- EK is lost and heat is produced
X-ray;
  0.1 nm
f  3 x 1018 Hz
Only _____________ X-ray photon is produced from _____________ einteraction with a _____________ energy level electron but
_____________ than one photon from one _____________ incident may be
produced.
http://www.colorado.edu/physics/PhysicsInitiative/Physics2000/xray/making_xrays2.ht
ml
The _____________ anode is typically made from _____________ tungsten
which is often _____________ in copper (to help heat conductivity)
and _____________ cooled to stop the tungsten from _____________.
P3A3B Atomic Physics Notes 2013
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Coghlan
Energy of electron:
W = q V
Highest energy x-ray
= q V
h fmax
= q V
fmax
= q V
h
fmax = q V
h
Where
fmax  maximum frequency of x-ray produced, Hz
q  charge on electron, C
V  acceleration potential difference, V
h  Planck’s constant, 6.63 x 10-34 J s
http://www.antonineeducation.co.uk/Physics_A2/Options/Module_6/Topic_7/topic_7_x.htm
Ex/
Calculate the cut-off wavelength for the X-ray spectrum produced
by electrons that are accelerated through a potential difference of
65.0 kV.
P3A3B Atomic Physics Notes 2013
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Applications of X-rays
http://www.colorado.edu/physics/PhysicsInitiative/Physics2000/xray/xray_abs1.html
http://www.colorado.edu/physics/PhysicsInitiative/Physics2000/xray/xray_abs2.html
http://www.colorado.edu/physics/PhysicsInitiative/Physics2000/xray/xray_abs3.html
http://www.colorado.edu/physics/2000/xray/
 Medical – the more _____________ the material the greater the xray _____________
- can vary the x-ray energy hence vary the image quality
- protection needed – _____________ radiation
- dentist – _____________ aprons
- veterinarians
- cancer treatment
 Industry – inspection of metal joins, welds, castings
 Crystallography – structure of molecules, crystals.