Particles and Radiation Flashcards
- Matter and radiation. -Quarks and leptons. - Quark phenomena.
Define atomic number, Z.
The number of protons in an atoms nucleus.
Define mass number, A.
The number of nucleons in its nucleus (protons+neutrons).
Define isotope.
Atoms of the same element with the same proton number, but a different neutron number.
Define specific charge.
Charge per unit mass (Ckg^-1).
What does the strong nuclear force do?
Overcomes the electrostatic force of repulsion between the protons in the nucleus, and keeps the protons, and neutrons together.
What is the specific size of the strong nuclear force’s range?
3-4fm.
When is the strong nuclear force attractive?
From 3-4fm to about 0.5fm.
When is the strong nuclear force repulsive?
At separations < 0.5fm, that acts to prevent neutrons and protons being pushed into each other.
How does the strong nuclear force effect like-nucleons?
It has the same effect between two protons or two neutrons as it does a proton and a neutron.
What does alpha radiation consist of?
Alpha particles which each comprise two protons and two neutrons (a He atom).
When an unstable nucleus of an element X emits an alpha particle, how is the nucleon number, A, and the atomic number, Z, effected?
The nucleon number decreases by 4 and the atomic number decreases by 2.
What does beta radiation consist of?
Fast-moving electrons.
What does an unstable nucleus of an element X emit when it has too many neutrons?
A B^- particle, (atomic number increases by 1).
What is also emitted during the emission of beta radiation?
An antiparticle with no charge called an antineutrino (represented by a v with a bar across the top).
What is gamma radiation?
Electromagnetic radiation emitted by an unstable nucleus.
What can gamma radiation pass through?
Thick metal plates.
When is gamma radiation emitted?
When the nucleus has too much energy.
Why were the neutrino and the antineutrino hypothesised?
To explain why beta particles from an isotope have a range of kinetic energies up to a maximum unlike alpha particles, which are emitted with a fixed proportion of the energy released.
When is B^+ radiation emitted?
When the nuclei have too many protons.
What speed do electromagnetic waves travel at in a vacuum?
The speed of light, c, (3.00 x 10^8)ms^-1.
Electromagnetic waves are emitted as short bursts of waves, each leaving the source in a different direction… What is the name of these bursts?
Photon.
What is rest energy?
When a particle is stationary, its rest mass corresponds to rest energy. Rest energy must be included in the conservation of energy.
For every type of particle there is corresponding antiparticle that:
- Annihilates the particle and itself if they meet, converting their total mass into photons.
- Has exactly the same rest mass as the particle.
- Has exactly opposite charge to the particle if the particle has a charge.
- Can be produced together with its corresponding particle in a process known as pair production. This can happen when a single photon with sufficient energy passing near a nucleus changes into a particle-antiparticle pair. The nucleus is necessary for conservation of momentum as well as conservation of energy.
What happens when a particle and corresponding antiparticle meet?
Their mass, including their rest mass, is all converted into radiation energy so that energy is conserved.
What is this process called?
Annihilation.
