Today
four particles are enough to describe most of things around us. Aristotle needed
four elements to describe the same. Has there been real progress in science?
Thomson proposed a theory, which explained the atomic structure using the
electron. This model was later found to be erroneous. Using scientific reasons
explain why it was accepted at the time.
Rutherford proposed the first nuclear model for the atom. With that model he
proved that the Thomson' theory was not correct. Comment on this case,
emphasizing how science works (observation, hypothesis, theory, news challenges...).
The Millikan experiment is considered among the ten best experiments in the
history of science. It would not have been possible if Roentgen had not
discovered the X-Rays. Why?
The De Broglie's equation allows us study the particles from its behavior as
waves. Using that equation, explain how increasing the particles' velocity
allows us to "see" smaller objects.
J. J. Thomson and his son G. P. Thomson represent "a kind of duality in the
family". What do we want to express with that comment?
The production of new particles from collisions in accelerators is based upon Einstein's equation. Explain why it is better to use
a circular accelerator than a linear accelerator.
The first techniques used to probe the structure of the atom came from the study
of the radioactivity. What were the different particles discovered and how could
they be separated?
In Rutherford's theory for the structure of the atom, it was necessary for the
electrons to be in the nucleus. What was the reason for that? Was this
assumption correct?
In 1925 Uhlenbeck and Goudsmit proposed a new property to understand the new
atomic spectra. Although that proposal was later thought to be incorrect, it was
important at that time. What was this new property and why was it not correct in
its first presentation?
One of the first detectors was the Cloud Chamber. Explain briefly how this
device works.
With detectors we can know the particle's kinetic
energy from the penetration length, and its momentum from the curvature using a
magnetic field. Using this information explain how the mass and charge of the
particle can be found.
Chadwick discovered the neutron in 1932. How could this particle be found if it
has no charge and therefore no tracks are produced in detectors?
When the muon was discovered, Isidor Rabi asked "who ordered that?"
Why were physicists surprised with the existence of this particle at that
moment?
P. A. M. Dirac combines, in 1928, Quantum Mechanics and Relativistic Theory. As a
result, two fundamentals topics are perfectly established. What are they?
Why was Pauli's proposal about neutrino existence out of the scientific
orthodoxy?
C. A. Anderson discovered the first anti-particle using balloons in the high
atmosphere. What was the reason to look for those particles at that altitude?
QED states that the interaction between particles is made through a special kind of
particle: the carrier particles are virtual particles that appear during
interaction and disappear after interaction. How can virtual particles be
understood from the laws of physics?
Why were the quarks necessary, in the 60's, for Particles Physics?
Quarks have a new quantum property called "color". What was the reason
to introduce this new property?