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Structure
Interesting Questions, Facts and Information
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Special Topics
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 Interesting Questions, Facts, and Information
 Atomic and Subatomic Physics
d. Each type of quark is represented by its first letter. (down quark equals d, charm quark equals c, etc.)
| True or False? In the theory of quark colour, a red quark will attract an 'anti-red' antiquark. | Subatomic Physics 1
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True . Yes, colour and opposite-colour will attract (explaining the mesons) and unlike colours will attract, with their attraction being maximised if they cluster in threes, one quark of each colour (explaining the baryons).
| True or False? In a baryon, three strange quarks cannot simultaneously occupy the lowest energy state. | Subatomic Physics 1
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False . It is false because there is ample evidence to suggest that the 'omega-minus' exists. This statement is true for three identical strange quarks. However, if quark colour is taken into account, it is possible for three strange quarks, each of different colour, to exist simultaneously in the lowest energy state.
| The 'omega-minus' consists of three strange quarks. What is its strangeness? | Subatomic Physics 1
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-3. The strangeness of a particle is defined as '-no. of strange quarks'. Each strange quark has charge 'minus one third' and therefore its charge is -1.
| Which physicist sucessfully predicted the existence AND the mass of the 'omega-minus' particle, using his theories on The Eightfold Way? | Subatomic Physics 1
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Murray Gell-Mann. Gell-Mann predicted the mass of this particle to 0.06 percent using the Eightfold Way patterns. This just shows the power of symmetries and patterns in physics.
Mesons and Baryons. Murray Gell-Mann and Yuval Ne'eman developed The Eightfold Way when they noticed patterns in the properties of the many known mesons and baryons.
| In 1935 Yukawa predicted the existence of the pi-meson. In which year was it finally discovered? | Subatomic Physics 1
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1947 . It was discovered by C. F. Powell, after a number of experiments studying cosmic rays in the French Pyrenees.
| The neutrino associated with the decay of a neutron was postulated in 1931 by which famous physicist? | Subatomic Physics 1
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Wolfgang Pauli . Wolfgang Pauli predicted this particle's existence after noticing anomalous energy losses in the beta decay of neutrons.
| One way to study cosmic rays is to use a cloud chamber. Who originally devised this piece of apparatus in 1911? | Subatomic Physics 1
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C. T. R. Wilson. When an electrically charged particle passes through supersaturated vapour, it ionises the vapour's atoms. Droplets of water settle on these ions and trace out the particle's trajectory. This is the principle of the cloud chamber.
up, up, down. Protons are composed of two up quarks and a down quark. Neutrons are made from two down quarks and an up quark.
| The final type of interaction is gravitational. Is it true that The Standard Model can account fully for gravitational interactions? | Subatomic Physics Made Easier
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No. Relativity is required for an adequate description of gravity. One of the advantages of string theory is its ability to deal with both relativity and quantum mechanics. Relativity is required for an adequate description of gravity. One of the advantages of string theory is its ability to deal with both relativistic and quantum mechanical considerations.
The basic outline of the fundamental particles operating in The Standard Model is as follows:
I. Mass Particles
A. Six quarks
1. Up, down, strange, charm, top, bottom
2. Combine to form Hadrons in two varieties: baryons, mesons
B. Six leptons
1. Three with charge (Tau, muon, electron)
2. Three neutrinos each corresponding to a charged lepton
3. Decay, don't combine
II. Three types of interactions mediated by force particles
A. Strong (gluons)
B. Electroweak
1. Electromagnetic (photon)
2. Weak (Z, W+, W- bosons)
C. Gravity (graviton?)
Beautifully simple, don't you think?
| The positive charges of the quarks within protons in atomic nuclei repel one another, and yet the strong force "glues" them together. What is the force particle exchanged in strong force interactions within the proton? | Subatomic Physics Made Easier
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Gluon. Each proton contains two quarks with a +2/3 charge and one with a -1/3 charge yielding a net charge of +1. The strong force is powerful enough to overcome the net repulsive force of the positively charged quarks which make up protons. The magnitude of the force actually increases with distance! It is difficult to detect individual quarks because so much energy is required to "pry" them out of the nucleus.
Pions mediate the residual strong nuclear force that binds the positively charged protons within the nucleus.
| The Standard Model accounts for particle interactions on the basis of exchanges of force particles. In the case of electromagnetic interactions, which force particle is exchanged? (Hint: the correct particle can be "light" in more than one sense.) | Subatomic Physics Made Easier
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Photon. Photons are the "coin-of-the-realm" in the electromagnetic world. An electron in an atomic orbital does nothing until it "absorbs" a photon emitted from some other particle. If the photon is the right energy, then the electron can absorb it and be "promoted" to a higher energy level. Later on that same electron can "emit" the photon and return to its prior energy level. The emitted photon can speed away to interact with another particle.
| There are six quarks, and they have been named up, down, top, bottom, charm and strange. What do we call the particles that quarks combine to form? (Hint: they HAD to call them something.) | Subatomic Physics Made Easier
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Hadrons. The strange and quirky names given to subatomic particles can intimidate and confuse the learner and obscure the simplicity of The Standard Model. Two of the quarks were initially named "truth" and "beauty". More sober minded physicists apparently prevailed, and truth and beauty became the top and bottom quark.
| According to The Standard Model, all that exists is composed of two varieties of fundamental particles. What are the commonplace, prosaic names given to these two categories of particles? | Subatomic Physics Made Easier
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Matter particles and force particles. The Standard Model uses matter and force particles to account for every atom, every subatomic particle and all the forms of force and energy.
| Marie Curie, one of the greatest physicists and chemists of all time, was ultimately killed by her work and discoveries which ironically saves so many lives in the modern age. As a result of Curie laying the foundations of radioactive study the humble smoke detector could evolve. Which form of radiation does the smoke detector use? | Quirky Quantum and Nuclear Physics
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Alpha Radiation. Marie Curie, who died of leukaemia, was an inspiration to generations of female scientists as she is one of the most decorated and celebrated physicists in history. Not only did she receive a Nobel Prize in 1903 for her work in the field of physics but also received a Nobel Prize for chemistry in 1911. This made her not just the first female recipient of a Nobel award but also the only person to receive a Nobel Prize in two different sciences in over 100 years! In a scientific discipline that is as traditionally male dominated as physics, her achievements and determination seem all the more inspiring.
The near ubiquitous smoke detector is an important use of alpha radiation (helium nuclei) and saves many lives worldwide each year. Within the smoke detector there is a radioactive source and a receiver which detects the flow of alpha particles. When smoke particles interrupt the flow, the receiver detects this and the alarm is sounded.
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| Physics isn't complete unless there are units involved and every student and fan of the science grow to cherish them. So, I think I will share my fondness with you! Experiments carried out have suggested that the diameter of an atomic nucleus is in the region of x10^-15m which is incomprehensibly small. What is the unit given to distances of around 10^-15m? | Quirky Quantum and Nuclear Physics
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Femtometre. As physicists encounter the increasingly large and the extremely small they need to have more extreme units to quantify exactly what it is we are observing or hypothesising. Such quantities are mind-boggling when we consider how difficult humans find splitting up even the tiny distance between one millimetre and the next on a ruler!
At the atomic level the units used are far smaller than the millimetre. The diameter of an entire atom is approximately x10^-10m which is given the name ångström after the Swedish physicist of the same name. Smaller again is the nuclear size of roughly x10^-15m which is a femtometre.
| Unstable nuclei form the basis of radioactivity and nuclear decay. Despite not being able to predict when an individual nucleus will decay it is possible to represent, via an exponential decay graph, what time related concept? | Quirky Quantum and Nuclear Physics
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Halflife. Halflife is defined as the time taken for half of the nuclei of a radioactive substance to decay. The concept of halflife is what characterises an exponential decay graph. As the halflife of a particular radioactive substance will predominantly be constant the gradient of the line on a graph will start at time = 0 and the percentage of undecayed nuclei will fall with a steep gradient. As more halflifes pass the gradient gets progressively less steep. Ultimately a curve will be formed.
| Using Einstein's theories (no calculations necessary), what can be said about the characteristics of a photon as it travels at the speed of light in a vacuum? | Quirky Quantum and Nuclear Physics
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The photon has no mass. It has been established that only things with zero mass are able to reach the speed of light and a photon is one such entity. There have been experiments undertaken by physicists which aim to accelerate particles to the speed of light, 'c'. However, they have realised that as the particle (which has a mass) approaches the speed of light, it gets increasingly difficult to provide the energy necessary to undergo further acceleration. They have also discovered that as the particle is accelerated extremely close to the value, 'c', the particle would need an infinite amount of energy to actually accelerate further to the value 'c'.
Albert Einstein. Albert Einstein is deified amongst scientific communities. His style, inimitable; his physical knowledge, paralleled by an elite few. A common misconception is that Albert Einstein received the Nobel Prize for his work on the Theory of Relativity. However, this is false as he received the prize not for his almost ubiquitously known equation, E = mc^2, but for his work on the photoelectric effect, a magnificently interesting field of particle physics.
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