Particle Physics Flashcards
What does the proton (atomic) number tell us?
How many protons are in the nucleus
What does the nucleon number tell us?
How many protons and neutrons are in the nucleus
How can you work out how many neutrons are in the nucleus?
Nucleon number - proton number
Why must the air be removed from the alpha particle scattering experiment?
So the alpha particles do not collide with air molecules
What did Rutherford conclude from the alpha particle scattering experiment?
The nucleus; is charged, contains most of the mass, is very small compared to the rest of the atom
What is thermionic emission?
Electrons can be released from the surface of a metal as it is heated
Why is it necessary to use high energy particles in particle accelerators?
Because low energy particles just bounce of each other
How are particles accelerated in a linear accelerator?
The first tube has a + charge. The electrons are attracted to the first tube. When half way in the tube, the first tube becomes - and the second tube becomes +. The electrons are repelled by the first tube and are attracted the the second tube
Why must the tubes in a linear accelerator get longer?
The time spent inside the tube must be constant. Because the electrons are accelerating, their speed is increasing.
Why must a linear accelerator be in a vaccum?
So the particles do not collide with any air molecules
How are particles accelerated in a cyclotron?
2 Dees. Electric field between the Dees. Particles are accelerated in the gap between the Dees. Whilst inside the Dees the particle will move in a circular path due to a magnetic field. As acceleration increases momentum, the radius increases
In a cyclotron, why does the p.d need to switch direction at exactly the moment the particle exits from the dee?
To maintain the accelerations at exactly the correct instant
In the bubble chamber, what does the radius of curvature tell us?
The mass and charge of the particles
If a particle track appears from nothing, what does this tell us?
Particles have been created
When does annihilation occur?
When a particle and its corresponding antiparticle meet. They will disappear and be replaced by the equivalent energy
In any particle interaction, what 5 factors are always conserved?
Mass-energy, momentum, charge, lepton number, baryon number
What is a fundamental particle?
Has no substructure
What are the similarities and differences between particles and antiparticles?
Same mass but all other properties are opposite
What is a baryon made up of?
3 quarks
What is a meson made up of?
Quark and anti-quark
Any particle which feels the strong force is called a …?
Hadron
Are bayrons and mesons, hadrons?
Yes
What is the conservation of mass-energy?
A reaction can overcome any mass difference by having the particles begin or end with more kinetic energy to make up the difference
What does relativistic mean?
Particles travelling to the speed of light
What are the characteristics of a neutrino?
Massless and no charge
What is meant by ionisation?
Electrons have been removed/added from a molecule
How can you deduce the charge of a particle in the bubble chamber?
Flemings left hand rule
In the bubble chamber, if there is no track what can be deduced about that particle?
It is neutral
What is meant by by a charge of +2/3?
2/3 the charge of an electron
What is the role of a magnetic field in a cyclotron? (3)
The M field is perpendicular to the force/motion
Provides a centripetal force
Radius increases as speed increases ( r=p/BQ )
What is the role of an electric field in a cyclotron? (3)
The E field causes the particles to accelerate across the Dees
Constant time period
P.D switches every half cycle
Why does an electron confined within a nucleus have a very high energy? (2)
The de Broglie wavelength would have to be a similar size as the nucleus
The nucleus is a lot smaller than the atom
What does relativistic mean?
Travelling close to the speed of light
In a particle accelerator, why must very high energies be used?
To overcome the strong repulsive forces
In a particle accelerator, how can you work out the frequency?
Equate E=mc^2 and E=hf
Outline the atomic process that produces emission spectra (3)
Electrons gain energy to get to an energy level
Drop back down to their original energy level
Release a photon with a certain energy
