Choose one of the following three Projects, write a 10-page
report
and prepare a short
presentation. A material suggestion is made for each project, but you
are invited to use any information you wish. You are expected to give a
"pedagogical" presentation covering the main points:
introduction, motivations, basic physics, applications, current status
and future prospects. The
presentation should last approximately 15-20 minutes and will be
followed
by questions and discussions. Students are encouraged to ask questions.
Project
1:
Quantum co-operation:
"... there are certain situations
in which the peculiarities of quantum mechanics can come out in a
special way on a large scale." Richard Feynman
Lasers: Yesterday, Today and tomorrow
"The laser may turn out to be
one of the most significant inventions of our times. A product of
quantum mechanics, it generates a light endowed with many remarkable
properties and qualitatively very different from the light hitherto
available to us from conventional sources. This form of light which
gives us a completely new tool for probing nature, already transforms
and broadens to an extraordinary extent the ancient science of optics.
It gives us a radically new power of control of light that opens up
seemingly limitless applications in arts and sciences, in medicine and
technology. Physicists have used lasers to study minute details of the
structure of atoms and molecules, to catch atoms in flight, and to
perform delicate experiments to test the very foundations of quantum
mechanics. Biologists have used lasers to study the structure and the
degree of aggregation of various biomolecules, to probe their dynamic
behaviour, or even to detect constitutents of cells. Mathematicians
actively involved with nonlinear complex systems have been intrigued by
the possibility that their ideas could be tested by observing the
dynamical instabilities exhibited by some lasers. And not only
scientists or engineers - artists and dentists, soldiers and spies have
also been touched by this invention." Invitation to Contemporary Physics, p.41.
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Material (suggestions):
New State of Matter Revealed: Bose-Einstein Condensate
A laser beam differs from the
light from an ordinary light bulb in
several ways. In the laser the light particles all have the same energy
and oscillate together. To cause matter also to behave in this
controlled way has long been a challenge for researchers. This year's
Nobel Laureates have succeeded – they have caused atoms to "sing in
unison" – thus discovering a new state of matter, the Bose-Einstein
condensate (BEC).
In 1924 the Indian physicist Bose made important
theoretical calculations regarding light particles. He sent his results
to Einstein who extended the theory to a certain type of atom. Einstein
predicted that if a gas of such atoms were cooled to a very low
temperature all the atoms would suddenly gather in the lowest possible
energy state. The process is similar to when drops of liquid form from
a gas, hence the term condensation.
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Seventy years were to pass before this
year's
Nobel Laureates, in 1995, succeeded in achieving this extreme state of
matter. Cornell and Wieman then produced a pure condensate of about 2
000 rubidium atoms at 20 nK (nanokelvin), i.e. 0.000 000 02 degrees
above absolute zero.
Independently of the work of Cornell and Wieman,
Ketterle performed corresponding experiments with sodium atoms. The
condensates he managed to produce contained more atoms and could
therefore be used to investigate the phenomenon further. Using two
separate BECs which were allowed to expand into one another, he
obtained very clear interference patterns, i.e. the type of pattern
that forms on the surface of water when two stones are thrown in at the
same time. This experiment showed that the condensate contained
entirely co-ordinated atoms. Ketterle also produced a stream of small
"BEC drops" which fell under the force of gravity. This can be
considered as a primitive "laser beam" using matter instead of light.
It is interesting to speculate on areas for the
application of BEC. The new "control" of matter which this technology
involves is going to bring revolutionary applications in such fields as
precision measurement and nanotechnology.
Material (suggestions):
Project
2: Microscopes to observe and manipulate matter ... and
to study the first nanoseconds after the Big Bang
From the Electron Microscope to the Scanning Tunneling Microscope
The development of the elctron
microscope began with work carried out by Ernst Ruska as a young student at
the Berlin Technical University at the and of the 1920's. He found that
a magnetic coil could act as a lens for electrons, and that such an
electron lens could be used to obtain an image of an object irradiated
with electrons. By coupling two electron lenses he produced a primitive
microscope. He very quickly improved various details and in 1933 was
able to build the first electron microscope with a performance clearly
superior to that of the conventional light microscope. Ruska
subsequently contributed actively to the development of commercial
mass-produced electron microscopes that rapidly found applications
within many areas of science.
Electron microscopy has since been developed through technical
improvements and through the advent of entirely new designs, among them
the scanning tunnelling electron microscope. A number of researchers
have taken part in both this and the earlier development, but Ruska's
pioneering work is clearly the outstanding achievement.
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Gerd Binnig and Heinrich
Rohrer design the first scanning tunneling microscope. This
instrument is not a true microscope (i.e. an instrument that gives a
direct image of an object) since it is based on the principle that the
structure of a surface can be studied using a stylus that scans the
surface at a fixed distance from it. Vertical adjustment of the stylus
is controlled by means of what is termed the tunnel effect - hence the
name of the instrument. An electrical potential between the tip of the
stylus and the surface causes an electric current to flow between them
despite the fact that they are not in contact. The strength of the
current is strongly dependent on the distance, and this makes it
possible to maintain the distance constant at approximately 10-7
cm (i.e. about two atom diameters). The stylus is also extremely sharp,
the tip being formed of one single atom. This enables it to follow even
the smallest details of the surface it is scanning. Recording the
vertical movement of the stylus makes it possible to study the
structure of the surface atom by atom.
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The scanning tunneling microscope is completely new, and we have so far
seen only the beginning of its development. It is, however, clear that
entirely new fields are opening up for the study of the structure of
matter. Binnig's and Rohrer's great achievement is that, starting from
earlier work and ideas. they have succeeded in mastering the enormous
experimental difficulties involved in building an instrument of the
precision and stability required.
Material (suggestions):
From the Electron Microscope to High Energy Particle Accelerators
- Higher Energies => Smaller Scales => Ultimate
constituents of matter
- Light from stars red-shifted Expansion and Cooling of
Universe
- Higher Energies <=> Higher Temperatures
=> Big-Bang
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Material (suggestions):
Project
3: The Mysteries of MASS
What is mass and where is the missing mass?
"Most people think they know what
mass is, but they understand only part
of the story. For instance, an elephant is clearly bulkier and weighs
more than an ant. Even in the absence of gravity, the elephant would
have greater mass - it would be harder to push and set in motion.
Obviously the elephant is more massive because it is made of many more
atoms than the ant is, but what determines the masses of the individual
atoms? What about the elementary particles that make up the atoms -
what determines their masses? Indeed, why do they even have mass?" Gordon K. Kane, Scientific American 2005.
For Newton, weight is proportional to mass.
For Einstein, mass is equivalent to energy. None explained th eorigin
of mass. The current theory - the Standard Model - say that elementary
particles acquire mass by interacting with a new kind of field - the
Higgs field - that permeates all of reality. Physicists
are hunting for an associated elusive particle - the Higgs boson.
Finding it will give us a more complete understanding about how
the universe works.
The extended Standard Model may also help solve the puzzle of the
invisible dark matter that accounts for about 25% of the Cosmos.
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Material (suggestions):
