6.4 Nuclear and Particle Physics Flashcards
what was Thompsons Plum Pudding Model
a model for the atom in which a neutral atom is made up of a uniform sphere of positive charge with tiny electrons embedded in it like the fruit in a plum pudding
how was Rutherfords alpha scattering experiment carried out
alpha particles were fired at s thin sheet of gold foul under a vacuum- the deflected alpha particles were detected on all sides by a ring of scintillators- materials that release photons when a particle hits them
what did Rutherford expect to happen
the particles would pass straight through the thin foil as the alpha radiation has such a high speed however he presumed that due to the wall of charge in their path they would on average be deflected to a large degree
what did Rutherford observe from his alpha scattering experiment
the majority of the particles passed straight through with only a slight deflection of on average only a degree
what can be deduced from Rutherfords alpha scattering experiment
the atom is mostly open space and so the mass must be concentrated at some point within the atom- this must be the nucleus
what suggested that the nucleus of an atom must be positive
a small proportion of the particles were deflected by more than 90° and the alpha particles are positively charged
what is the Rutherford model
the atom has a small dense nucleus which contains most of the mass of the atom and is positively charged and was surrounded by orbitting negative electrons which make the overall charge of the atom neutral
what is an isotope
atoms of the same element with differing numbers of neutrons
why do isotopes undergo the same chemical reactions but different nuclear reactions
their electronic configurations being identical however the stability of their nuclei may differ greatly
what is a nucleon
a subatomic particle that resides in the nucleus of the atom and so is either a proton or a neutron
how many protons an electrons does an atom have
a proton has a charge that is equal and opposite to that of an electron and so an atom must have an equal number of protons as electrons to remain neutral
what are the subatomic constituents of an atom represented with
the atomic or proton number Z and the mass number A- the mass number (also known as the nucleon number) is simply a sum of the number of protons and neutrons in the nucleus
how can an estimate from the mass of an atom be gained
by multiplying the mass number by the atomic mas unit
what is the atomic mass unit
one twelfth the mass of carbon-12 [u] (1.661x10^-27kg)
how can the radius of a nucleus be determined
R=r0A^1/3
R= radius of nucleus
r0= constant 1.2fm (1.2x10^-15)
A= atomic mass
what are the four fundamental forces in the universe
-gravitational force
-electromagnetic force
-weak nuclear force
-strong nuclear force
what is the gravitational force and what are its properties
-acts on particles with mass
-it is always attractive
-has in infinite range
-very weak
what is the electromagnetic force and what are its properties
- acts on particles with charge
- has an infinite range
what is the weak nuclear force and what are its properties
- the force responsible for beta decay
- changes quark types
- very short range
what is the strong nuclear force and what are its properties
-acts between all nucleons and all quarks
-counteracts the repulsive electrostatic forces between protons in the nucleus
-attractive up to 3fm
-repulsive below 0.5fm
-has a limited range
what is the mass-energy equivelence
mass can be thought of as energy in the form of mass-energy
what is Einsteins relation
energy change is proportional to the mass change and that the constant of proportionality is the speed of light squared
what is the formula for Einsteins relation
∆E=∆mc^2
∆E= change in energy
∆m= change in mass
c= the speed of light in a vacuum
how is the concept of mass as a form of energy demonstrated
through annihilation of matter and antimatter where the combined mass of two particles is related by the mass-energy equivalence to the energy released in the annihilation event
what is the rest mass of an object
mass of an object at rest
why is rest mass significant
as any object, given high enough energy can acquire incredibly high mass, the only true measure of mass, the only agreed upon by all observers is the mass of that object at rest
why is the theory that energy has mass not so significant
the change is mass is extremely small for low speed as a forctor of the inverse speed of light squared is the constant of proportionality (x10^-17)
what is binding energy
minimum energy required to completely separate a nucleus into its constituent protons and neutrons
what is the mass defect of a nucleus
the difference between the mass of the completely separated nucleons and the mass of the nucleus
Binding energy
FILL REST
what is an antiparticle
a particle will have an antiparticle which will have an equal mass to it it opposite charge
what happens when a particle and an antiparticle interact
as they are oppositely charged they are attracted to eachother and as they meet at a point in space, the annihilate to produce energy in the form of photons
what is pair production
when a high energy photon creates a matter-anti matter pair
how does pair production occur
when a photon has an energy greater than the combined rest masses of the two particles
what is the unit for rest mass
MeV/c^2
what two groups do fundamental particles consist of
hadrons and leptons
What are hadrons made up of
Fundamental particles called quarks
What forces are hadrons acted on by
The strong and the weak nuclear force
What’s the only way that quarks can exist
In quark-antiquark pairs
What are mesons
A quark-antiquark pair
What are baryons
Groups of 3 quarks and antiquarks
What are examples of baryons
Protons and neutrons
What’s the charge of quarks
Quarks have fractional charges of the elementary charge- ± 1/3e or ± 2/3e
Why have only whole numbers of elementary charge been observed
Quarks cannot be isolated and always combine to form mesons or baryons which have whole number charges
How has the existence of quarks been deduced
Particle collisions
How were particle collisions used to deduce the existence of quarks
kinetic energy and mass-energy of the particles can be transferred into other forms and particles created or destroyed by the mass-energy equivelence
kinetic energy and mass-energy of the particles can be transferred into other forms and particles created or destroyed by the mass-energy equivelence
